Everything We Know About Microsoft Exchange Server SE (Subscription Edition)

Introduction to Exchange Server Subscription Edition

Microsoft Exchange Server has been a cornerstone of business communication since its initial release in 1993. As we approach the release of Exchange Server Subscription Edition (SE) in the third quarter of 2025, we’re seeing a significant shift in Microsoft’s approach to on-premises email and collaboration services. This new edition represents not just an update to the software, but a shift in how Exchange Server will be licensed, deployed, and maintained going forward.

Exchange Server has undergone numerous transformations over its three-decade history. From its first public release as Exchange 4.0 in 1996, through versions like Exchange 2000 (which introduced instant messaging and Active Directory integration), Exchange 2007 (which brought PowerShell integration and multiple database HA options), to Exchange 2019 (which enabled installation on Windows Server Core). Each iteration has expanded capabilities while maintaining the core mission of providing reliable email and collaboration services.

Instant detection of emerging threats for Exchange

FEATURED SECURITY PRODUCT, powered by Messageware

Table of Contents:

Licensing Structure of Exchange Server SE
Pricing and Subscription Models
Upgrade Paths to Exchange Server SE
Technical Requirements and Prerequisites
Key Features and Improvements
Integration with Microsoft 365 and Hybrid Deployments
Maintenance and Updates
Licensing Considerations for Enterprise Agreement Customers
Security and Compliance
Integration with Microsoft Sentinel
Summary
References and Additional Resources

Brief History of Exchange Server

Exchange Server’s development began in 1993 with a private preview, followed by the first publicly available version, Exchange 4.0, in 1996. Subsequent major releases included:

1997: Exchange 5.0 introduced SMTP and Office Web Access
1998: Exchange 5.5 added Standard and Enterprise editions and support for IMAP4
2000: Exchange 2000 brought instant messaging and AD integration
2003: Exchange 2003 improved migration capabilities
2007: Exchange 2007 introduced PowerShell integration and unified messaging
2010: Exchange 2010 introduced Database Availability Groups (DAGs)
2013: Exchange 2013 added tighter integration with Office services
2016: Exchange 2016 removed separate server roles except Edge Transport
2019: Exchange 2019 enabled installation on Windows Server Core

Transition from Perpetual Licensing to Subscription Model

The most significant change with Exchange Server SE is the move from perpetual licensing to a subscription-based model. Unlike previous versions that required a one-time purchase, Exchange Server SE will operate on a yearly subscription basis. This aligns with Microsoft’s broader strategy of shifting its software products to subscription services.

Under the new model, organizations will need either active Software Assurance (SA) to use the product or will need to purchase subscription licenses. If Software Assurance lapses, customers will retain rights only to the 2019 version of the product. This represents a “forced march from Exchange perpetual licensing to a subscription-only model,” as Microsoft announced in its Exchange Server Roadmap in May 2024.

Learn about licensing options for Exchange Server 2019 here.

Key Differences Between Exchange Server SE and Previous Versions

Exchange Server SE introduces several key differences compared to its predecessors:

Licensing Structure: The shift to subscription-based licensing is the most obvious change, moving from capital expenditure to operational expenditure.
Continuous Updates: Subscribers will receive all the latest feature updates, security patches, and bug fixes as part of their subscription, eliminating the need to purchase new versions every few years.
Update Cadence: Once a server is running Exchange Server SE, it will follow an update cadence of two Cumulative Updates (CUs) per year.
Compatibility Changes: Exchange Server SE will not support coexistence with Exchange 2013, and by the time Exchange Server SE CU1 is released in late 2025, it will block coexistence with all unsupported versions (Exchange 2013, 2016, and 2019).
Operating System Support: Exchange Server SE will support Windows Server 2019, Windows Server 2022, and Windows Server 2025.

Microsoft’s Strategic Shift Toward Subscription-Based Services

Exchange Server SE is part of Microsoft’s broader strategic shift toward subscription-based services across its product portfolio. This transition began with the introduction of Office 365 in 2010 and has gradually expanded to include more of Microsoft’s server products.

The subscription model offers Microsoft several advantages, including more predictable revenue streams and the ability to deliver continuous improvements rather than major version releases every few years. For customers, the subscription approach promises predictable annual costs, making it easier to budget for IT infrastructure.

This shift reflects Microsoft’s recognition that many organizations still require on-premises solutions due to regulatory requirements, data sovereignty concerns, or existing infrastructure investments, even as cloud adoption grows. Exchange Server SE provides these organizations with a way to maintain on-premises email solutions while benefiting from a more modern licensing and update model.

As we approach the release of Exchange Server SE in Q3 2025, organizations currently running Exchange 2016 or 2019 should begin planning their upgrade strategies, particularly since Exchange 2019 CU15 will be the last “version” of the perpetual license of on-premise Exchange.

Licensing Structure of Exchange Server SE

Exchange Server Subscription Edition (SE) introduces a significant shift in Microsoft’s licensing approach for on-premises email servers. This new licensing structure aligns with Microsoft’s broader strategy of moving customers toward subscription-based services while still accommodating organizations that need to maintain on-premises infrastructure.

Overview of the Subscription-Based Model

Exchange Server SE adopts a subscription-based licensing model, replacing the traditional perpetual licensing structure used in previous versions. Under this model, organizations must pay for annual subscriptions rather than making a one-time purchase. This approach provides continuous access to the latest features and security updates as long as the subscription remains active.

The subscription model follows the same structure as SharePoint Server SE, requiring either active Software Assurance (SA) or qualifying Microsoft 365 subscriptions to use the product.

Comparison with Previous Perpetual Licensing

The shift from perpetual licensing to subscription-based licensing marks a significant departure from how Exchange Server was previously licensed:

Perpetual Licensing (Exchange 2019 and earlier):

One-time purchase that granted indefinite usage rights
Major version upgrades required new license purchases
Security updates provided during the support lifecycle
Capital expenditure (CAPEX) budgeting model
No ongoing license validation requirements

Subscription Licensing (Exchange Server SE):

Recurring payments (annual subscription)
Continuous updates included with active subscription
Operational expenditure (OPEX) budgeting model
License rights contingent on maintaining active subscription
Access revoked if subscription or SA lapses

If SA lapses, customers retain rights only to Exchange Server 2019, not the new SE version.

Software Assurance (SA) Components and Benefits

Software Assurance is a critical component of the Exchange Server SE licensing structure, offering several benefits to organizations:

Upgrade Rights: Active SA provides automatic eligibility to upgrade to Exchange Server SE upon release
Continuous Updates: Guaranteed access to biannual cumulative updates (CUs) and security patches
Technical Support: 24/7 support services for critical issues
Training and Resources: Access to training materials and deployment resources
License Mobility: Flexibility to reassign licenses across server farms
Transition Path: Provides a cost-effective transition by leveraging existing license investments

Organizations with active SA on their existing Exchange 2019 licenses will have a smoother transition path to Exchange Server SE compared to those without SA coverage.

Server Licensing Requirements

Exchange Server SE follows the Server/CAL licensing model, similar to previous versions. The server licensing requirements include:

Server License: Each running instance of Exchange Server SE requires a server license. Microsoft will increase standalone server license prices by 10% starting July 1, 2025.
License Management: Customers will manage software and product keys via the Microsoft 365 admin center, which replaces the Volume Licensing Service Center.

Licensing Paths: Organizations have two primary licensing paths:

On-premises licensing: Purchase Exchange Server SE license for each running instance plus CALs for each user/device, with active SA required
Cloud subscription licensing: If all users accessing on-premises Exchange Server SE have qualifying cloud subscriptions (Microsoft 365 E3/E5), SA is not required

Hybrid Configuration: Microsoft will continue to provide a free license via Hybrid Configuration Wizard for servers used exclusively for recipient management, though this still requires active SA or qualifying cloud subscriptions to receive updates.

Client Access Licenses (CALs) Structure

In addition to server licenses, Exchange Server SE requires Client Access Licenses (CALs) for each user or device accessing the server. The CAL structure includes:

Licensing Models:

User CALs: License a person to access Exchange from any device, ideal when users outnumber devices
Device CALs: License a specific device for Exchange access, economical for shared workstations

CAL Requirements:

Any authenticated access to Exchange requires a CAL, including remote access through mobile devices
CALs are valid only for your organization’s Exchange servers, not for non-affiliated organizations
A user with multiple mailboxes requires only one CAL, while multiple users accessing the same mailbox each need their own CAL

Price Increases: Starting July 1, 2025, Microsoft will increase prices for:

Core CAL Suite by 15%
Enterprise CAL Suite by 20%

Standard vs. Enterprise CALs

Exchange Server SE maintains the distinction between Standard and Enterprise CALs, each providing access to different feature sets:

Standard CAL Features:

Email, shared calendaring, contacts, and tasks management
Outlook Web Access
Exchange ActiveSync
Managed Default Folders

Standard CALs can be acquired as standalone purchases or as part of product suites like Core CAL Suite.

Enterprise CAL Features:

The Enterprise CAL is an “additive” CAL purchased only after acquiring the Standard CAL. Together, they enable access to all Exchange features, including:

Advanced Exchange ActiveSync Policies
Unified Messaging
Per-User and Distribution List Journaling
Managed Custom Folders
Advanced security features

Features Available with Different License Types

The features available to organizations depend on the combination of server licenses and CALs:

Exchange Server SE with Standard CALs:

Core email and calendaring functionality
Basic mobile device management
Standard security features
Web access through Outlook Web App

Exchange Server SE with Enterprise CALs:

All Standard CAL features
Advanced compliance capabilities
Advanced security features
Advanced mobile device management policies
Unified messaging capabilities

Exchange Server SE with Microsoft 365 E3/E5:

All Enterprise CAL features
Integration with cloud services
Simplified license management
Potential cost savings for organizations already invested in Microsoft 365

This tiered approach allows organizations to select the licensing combination that best meets their specific needs and budget constraints while maintaining compliance with Microsoft’s licensing requirements.

Pricing and Subscription Models

The transition to Exchange Server Subscription Edition (SE) brings significant changes to Microsoft’s pricing structure for on-premises email solutions. These changes reflect Microsoft’s strategic shift toward subscription-based services while maintaining options for organizations that require on-premises deployments.

Annual Subscription Costs

Microsoft has announced several pricing changes that will take effect on July 1, 2025, coinciding with the general availability of Exchange Server SE:

Server License Increase: Standalone server licenses for Exchange Server SE will increase by 10% compared to Exchange Server 2019 pricing
Core CAL Suite Increase: Prices for the Core CAL Suite will rise by 15%
Enterprise CAL Suite Increase: The Enterprise CAL Suite will see the largest increase at 20%

While Microsoft hasn’t published specific dollar amounts for these licenses, we can estimate based on previous pricing structures. For example, if an Exchange Server 2019 license previously cost approximately $700, the new Exchange Server SE license would cost around $770 after the 10% increase.

Similarly, Enterprise CALs that previously cost around $130 per user would increase to approximately $156 per user with the 20% price hike. Software Assurance (SA) costs are typically calculated as 25% of the license price annually, resulting in additional expenses for organizations that choose this path.

Comparison with Previous Exchange Server Versions

The pricing model for Exchange Server SE differs fundamentally from previous versions in several ways:

Perpetual vs. Subscription: Previous versions like Exchange 2016 and 2019 used a perpetual licensing model with a one-time purchase, while Exchange Server SE requires ongoing subscription payments.
CAPEX to OPEX Shift: This change represents a shift from capital expenditure (CAPEX) to operational expenditure (OPEX), requiring adjustments to budgeting processes and financial planning.
Continuous Licensing Requirement: Unlike previous versions where organizations could continue using the software indefinitely after purchase (even after support ended), Exchange Server SE requires maintaining active subscriptions or Software Assurance to retain access.
Update Delivery: With Exchange Server SE, all updates are included in the subscription cost, eliminating the need to purchase new versions every few years.

Licensing Options for Different Organizational Sizes

Microsoft offers different licensing paths to accommodate organizations of various sizes:

Small Organizations (Under 50 Users):

For small businesses without existing Software Assurance, the initial costs include both the server license and CALs, plus the SA component for each
A typical 50-user organization might expect first-year costs of approximately $10,700 ($963 for server license with SA plus $9,750 for 50 Enterprise CALs with SA)
Small organizations may find Microsoft 365 more cost-effective than maintaining on-premises Exchange Server SE, especially when considering hardware and management costs

Medium Organizations (50-500 Users):

Medium-sized businesses typically benefit from volume licensing discounts
Organizations in this range often consider hybrid deployments, using free hybrid server licenses for recipient management while gradually transitioning users to Exchange Online

Large Organizations (500+ Users):

Enterprise Agreement (EA) customers often have negotiated discounts and may find maintaining on-premises Exchange more cost-effective, especially with existing hardware investments
Large organizations with Microsoft 365 E3/E5 licenses for all users can deploy Exchange Server SE without additional SA requirements, making this an attractive option for enterprises already invested in Microsoft’s cloud ecosystem

Cost Considerations for Migrations

When planning a migration to Exchange Server SE, organizations should consider several cost factors beyond just licensing:

Software Assurance Requirements: Organizations must maintain active SA on both server licenses and CALs to remain compliant and receive updates. Without SA, organizations lose access to Exchange Server SE and revert to Exchange 2019 rights.
Infrastructure Investments: Depending on the current environment, hardware upgrades or additional resources may be necessary to support Exchange Server SE.
Migration Strategy Costs: Organizations transitioning from older versions like Exchange 2016 may need to perform a two-step upgrade (first to Exchange 2019 CU15, then to Exchange SE), potentially increasing migration complexity and costs.
Training and Support: IT staff may require additional training to manage the new subscription model and features, representing an often-overlooked cost component.
Hybrid Deployment Savings: Organizations can leverage free hybrid server licenses for recipient management when configured through the Hybrid Configuration Wizard, potentially reducing costs during migration periods.
Microsoft FastTrack Support: Eligible organizations migrating to Exchange Online instead of Exchange Server SE can access Microsoft FastTrack services at no additional cost, providing migration assistance and potentially reducing implementation expenses.
Budget Planning Shift: Organizations need to adjust from one-time capital expenses to recurring operational expenses, requiring changes to budgeting processes and potentially affecting cash flow planning.

The pricing structure for Exchange Server SE represents Microsoft’s continued commitment to supporting on-premises deployments while encouraging a gradual transition to cloud services. Organizations should carefully evaluate their specific needs, existing investments, and long-term strategy when deciding between maintaining on-premises Exchange Server SE or migrating to Exchange Online.

Upgrade Paths to Exchange Server SE

With Exchange Server SE scheduled for release in the third quarter of 2025, organizations must carefully plan their upgrade strategy. Microsoft has defined two distinct upgrade paths to Exchange Server SE, each with its own requirements, benefits, and limitations.

In-place Upgrade Options from Exchange Server 2019

The in-place upgrade path represents a significant advancement in Microsoft’s approach to Exchange Server upgrades, offering a streamlined transition for organizations currently running Exchange Server 2019:

Eligibility Requirements: This option is available exclusively for organizations running Exchange Server 2019 CU14 or CU15. Organizations on older Cumulative Updates must first update to CU14 or CU15 as a prerequisite.
Simplified Process: Microsoft describes the in-place upgrade as “identical to installing a CU”, making it substantially less complex than traditional Exchange Server version upgrades.
Risk Assessment: Microsoft has explicitly characterized the in-place upgrade as a “low risk” operation, addressing concerns from customers who might view this streamlined approach as “too good to be true.”
Minimal Disruption: The in-place upgrade eliminates the need for new hardware, mailbox migrations, or namespace changes, making it the fastest and least disruptive upgrade option.

Process Similar to Applying Cumulative Updates (CUs)

The in-place upgrade to Exchange Server SE follows a familiar process for Exchange administrators:

Installation Experience: The process mirrors the well-established procedure for installing Cumulative Updates, which most Exchange administrators perform regularly.
Server Transformation: When completed, the upgrade transforms Exchange 2019 servers into Exchange SE servers while maintaining all existing configurations and mailboxes.
Downtime Requirements: Like standard CU installations, the process requires taking servers offline temporarily but does not involve the extended migration periods associated with traditional version upgrades.
Rollback Options: As with CU installations, organizations should have appropriate backup and recovery procedures in place, though Microsoft’s characterization of the process as “low risk” suggests confidence in its reliability.

Legacy Upgrade Process

For organizations that cannot use the in-place upgrade path, the legacy upgrade process provides a more traditional approach:

Mandatory Scenarios: This approach is required for organizations running Exchange 2016 or earlier versions, as well as those seeking to change their underlying operating system or hardware.
Traditional Migration: The legacy upgrade involves “introducing the newer server into the organization, moving all mailboxes and resources from older servers to new servers and uninstalling the old servers”.
Greater Complexity: This method is more complex and time-consuming than the in-place upgrade, requiring careful planning and execution across multiple phases.

Requirements for Hardware Refresh or OS Upgrades

Organizations considering hardware or operating system changes must understand several key constraints:

No In-place OS Upgrades: Microsoft explicitly does not support in-place upgrades of the underlying Windows OS on Exchange servers. This restriction applies to all Exchange versions, including Exchange Server SE.
OS Options: Exchange Server SE supports Windows Server 2019, Windows Server 2022, and Windows Server 2025, providing flexibility for organizations planning new deployments.
Server Core Support: Unlike previous versions, Exchange Server SE fully supports installation on Server Core, which Microsoft now recommends as the preferred deployment option.
Hardware Requirements: The hardware requirements for Exchange Server SE remain consistent with those of Exchange 2019 CU15, minimizing the need for hardware upgrades for organizations already running recent Exchange versions.

Building New Infrastructure

Organizations opting for the legacy upgrade path will need to establish a new Exchange Server SE environment:

Server Deployment: This involves installing Exchange Server SE on new servers with supported operating systems, typically Windows Server 2022 or Windows Server 2025.
Configuration Requirements: The new environment must be properly configured to coexist with the existing Exchange organization during the transition period.
Service Configuration: All necessary services, including transport, client access, and mailbox services, must be properly configured and tested before migrating production workloads.

Mailbox Migration Strategies

The legacy upgrade path requires careful planning for mailbox migrations:

Migration Methods: Organizations can use standard Exchange mailbox move requests to transfer mailboxes from older servers to Exchange Server SE.
Batch Processing: For large organizations, implementing a phased migration approach with carefully planned batches helps minimize disruption and manage resource utilization.
User Communication: Effective communication with end users about migration timing and potential impacts is essential for a smooth transition.
Post-Migration Verification: Testing and verification procedures ensure all mailbox data and functionality are properly preserved after migration.

Namespace Reconfiguration

Organizations performing legacy upgrades may need to reconfigure their Exchange namespaces:

URL Planning: Careful planning of internal and external URLs for services like Outlook Web App, ActiveSync, and Autodiscover ensures continuity during and after the migration.
Certificate Management: SSL certificate updates may be required to accommodate new server names or namespace changes.
DNS Adjustments: DNS records must be updated appropriately to direct clients to the new Exchange Server SE infrastructure.

Coexistence Limitations with Older Exchange Versions

Microsoft has established clear boundaries regarding coexistence between Exchange Server SE and older versions:

Exchange 2013 Compatibility: Exchange Server SE does not support coexistence with Exchange 2013. Organizations must remove all Exchange 2013 servers before installing Exchange 2019 CU15 or Exchange Server SE.
Exchange 2016/2019 Coexistence: Exchange Server SE RTM will support coexistence with Exchange 2016 and Exchange 2019, allowing for phased migrations.
CU1 Restrictions: Once Exchange Server SE CU1 is released (expected in late 2025), it will block coexistence with all previous versions, including Exchange 2016 and Exchange 2019. At this point, all servers in the organization must run Exchange Server SE.
Migration Timeline Pressure: With only four months between Exchange Server SE’s release and Exchange 2016’s end of support, organizations still running Exchange 2016 face significant time pressure to complete their migrations.

These coexistence limitations create a clear timeline for organizations to complete their migrations to Exchange Server SE, with all previous versions becoming unsupported and incompatible once Exchange Server SE CU1 is released.

Technical Requirements and Prerequisites

Understanding the technical requirements and prerequisites for Exchange Server SE is essential for organizations planning their deployment or migration. Microsoft has maintained consistency with many of the requirements from Exchange 2019, while introducing some new considerations specific to the subscription edition.

Hardware Requirements

Exchange Server SE maintains the same hardware requirements as Exchange Server 2019 CU15, providing a clear upgrade path for organizations with existing Exchange 2019 deployments:

Processor: 64-bit Intel processor that supports Intel 64 architecture (x64). While a single processor is the minimum requirement, dual processors running at 2.0 GHz or faster are recommended for production environments.

Memory (RAM):

Mailbox Server Role: 128 GB minimum recommended
Edge Transport Role: 64 GB minimum recommended
Exchange Server SE supports large memory configurations up to 256 GB

Paging File Size: Microsoft recommends setting both the minimum and maximum paging file size to 25% of installed memory.

Disk Space: Sufficient disk space is required for the Exchange installation, logs, and databases. The base installation requires approximately 30 GB of free space.

Network Interface Cards: At least one network interface card per server, though multiple NICs are recommended for redundancy and network segmentation.

Screen Resolution: 1024 x 768 pixels (XGA) or higher.

File System: NTFS is required for all partitions containing Exchange files.

Operating System Compatibility

Exchange Server SE supports several Windows Server versions, offering flexibility for organizations with different infrastructure requirements:

Windows Server 2019 (Standard or Datacenter edition)
Windows Server 2022 (Standard or Datacenter edition)
Windows Server 2025 (Standard or Datacenter edition)

Microsoft does not support in-place upgrades of the operating system between major versions (for example, from Windows Server 2019 to Windows Server 2022) on servers with Exchange installed. Organizations planning OS upgrades must use the legacy migration approach rather than in-place upgrades.

Unlike previous versions, Exchange Server SE fully supports installation on Server Core, which Microsoft now recommends as the preferred deployment option for enhanced security and reduced attack surface.

Software Dependencies

Exchange Server SE requires several software dependencies to function properly:

.NET Framework:

For Windows Server 2019: .NET Framework 4.8
For Windows Server 2022 and 2025: .NET Framework 4.8.1 (recommended) or .NET Framework 4.8

Visual C++ Redistributable Package for Visual Studio 2012: Required for both mailbox and Edge Transport server roles.

Remote Server Administration Tools (RSAT): For Active Directory Domain Services (ADDS), installed using PowerShell command: Install-WindowsFeature RSAT-ADDS.

Active Directory Lightweight Directory Services (AD LDS): Required for Edge Transport servers, installed using PowerShell command: Install-WindowsFeature ADLDS.

Windows PowerShell: Exchange Server SE supports only the version of PowerShell included with Windows Server. It does not support Windows Management Framework (WMF) add-ons or other versions of PowerShell.

Network Infrastructure Requirements

Proper network configuration is critical for Exchange Server SE deployment:

IP Addressing: Static IP addressing is recommended for all Exchange servers to ensure consistent connectivity.

Domain Controller Requirements: While Exchange Server SE can coexist with domain controllers, Microsoft recommends against installing Exchange on Active Directory servers for security and performance reasons. Exchange should be installed only on member servers.

Active Directory Requirements:

Minimum domain functional level: Windows Server 2012 R2
AD schema: Unchanged from Exchange 2019 CU15

DNS Configuration: Proper DNS configuration is essential for client connectivity and server-to-server communication.

Stop AD Account Lockouts – Exchange Servers

FEATURED SECURITY PRODUCT, powered by Messageware

Security Considerations

Exchange Server SE introduces enhanced security requirements and best practices:

TLS Configuration: All Exchange servers in the organization must use consistent TLS configurations. If one server uses TLS 1.2, all servers must be configured to use TLS 1.2 to prevent connection failures.

Registry Settings: The following registry values must be explicitly set to 1 across all Exchange servers:

SchUseStrongCrypto
SystemDefaultTlsVersions

Windows Extended Protection: Exchange Server SE supports Windows Extended Protection, which enhances authentication security and mitigates authentication relay or man-in-the-middle attacks.

Authentication Changes: Starting with CU1 (expected late 2025), Exchange SE will enforce modern authentication protocols:

NTLM authentication will be deprecated in favor of Kerberos (Negotiate:Kerberos)
Organizations should update authentication methods and validate all mail routing paths

Protocol Security: Exchange SE will enforce hardened security defaults, requiring organizations to update from legacy protocols to more secure alternatives.

Server Core Recommendation: Microsoft recommends deploying Exchange Server SE on Windows Server Core to reduce the attack surface and enhance security.

These technical requirements and prerequisites provide the foundation for a successful Exchange Server SE deployment, whether organizations are performing an in-place upgrade from Exchange 2019 or implementing a new Exchange environment using the legacy approach.

Key Features and Improvements

Exchange Server Subscription Edition (SE) builds upon the foundation of Exchange Server 2019 while introducing several key improvements and features. As Microsoft’s final on-premises Exchange release, SE focuses primarily on lifecycle stability, security, and supportability rather than introducing a wide array of new features.

New Features Exclusive to Exchange Server SE

While Exchange Server SE is built on Exchange 2019 CU15 and offers similar core functionality, it does introduce several new capabilities:

Modern Lifecycle Policy: Unlike previous versions that followed the Fixed Lifecycle Policy with predetermined support dates, Exchange Server SE adopts the Modern Lifecycle Policy. This provides more flexible support timeframes with a minimum 30-day notification before required actions and 12 months to 3 years notice before end of support.
REST-based Admin API: Starting with CU1, Exchange Server SE will introduce a set of REST-based APIs to replace the deprecated Remote PowerShell (RPS) protocol. This aligns with the management approach already used in Exchange Online and provides a more modern administrative interface.
Authentication Protocol Changes: Exchange SE will change the default authentication protocol from NTLMv2 to Kerberos, enhancing security and aligning with modern authentication standards.
Windows Extended Protection: Exchange Server SE includes enhanced support for Windows Extended Protection, which mitigates authentication relay or man-in-the-middle attacks through channel-binding information specified via Channel Binding Tokens (CBT).

Security Enhancements

Security is a primary focus area for Exchange Server SE, with several important enhancements:

Extended Protection Enabled by Default: Unlike previous versions where it was optional, Windows Extended Protection is enabled by default during Exchange Server SE installation. This feature enhances authentication security by mitigating authentication relay and man-in-the-middle attacks.
Hardened Security Defaults: Exchange SE enforces stricter security defaults, requiring organizations to update from legacy protocols to more secure alternatives. This includes the deprecation of NTLM authentication in favor of Kerberos (Negotiate:Kerberos).
TLS Configuration Consistency: Exchange Server SE requires consistent TLS configurations across all servers in the organization. If one server uses TLS 1.2, all servers must be configured to use TLS 1.2 to prevent connection failures.
Server Core Recommendation: Microsoft recommends deploying Exchange Server SE on Windows Server Core to reduce the attack surface and enhance security, a capability that was introduced in Exchange 2019 but is now fully supported and recommended.

Performance Improvements

Exchange Server SE maintains the performance improvements introduced in Exchange 2019, including:

Improved Search Infrastructure: The search architecture in Exchange Server SE builds on the completely rebuilt search infrastructure first introduced in Exchange 2019. This architecture, originally designed for cloud scale and reliability in Exchange Online, allows for indexing of larger files, simpler management, and better search performance.
Faster, More Reliable Failovers: The enhanced search architecture results in significantly faster and more reliable failover between servers, improving overall system resilience.
Metacache Database: Exchange Server SE continues to leverage improvements to the core database engine that enable better overall performance and take advantage of the latest storage hardware, including larger disks and SSDs.
Modern Hardware Support: Exchange Server SE supports up to 256 GB of memory and 48 CPU cores, allowing organizations to leverage modern server hardware for improved performance.
Dynamic Database Cache: The information store process employs dynamic memory cache allocation, optimizing memory usage based on active database usage.

Cloud Integration Capabilities

Exchange Server SE enhances hybrid deployment scenarios, providing a bridge between on-premises and cloud environments:

Hybrid Deployment Support: Exchange Server SE fully supports hybrid deployments, enabling seamless integration with Exchange Online for organizations that want to transition to the cloud gradually.

Free Hybrid License: Microsoft continues to provide a free license via the Hybrid Configuration Wizard for servers used exclusively for recipient management, though this still requires active SA or qualifying cloud subscriptions to receive updates.

Hybrid Features: A hybrid deployment with Exchange Server SE provides secure mail routing between on-premises and Exchange Online organizations, mail routing with a shared domain namespace, unified global address list, free/busy and calendar sharing, centralized mail flow control, and a single Outlook on the web URL.

Cloud-based Archiving: Exchange Server SE continues to support Exchange Online Archiving for on-premises mailboxes, allowing organizations to leverage cloud storage for archiving while maintaining primary mailboxes on-premises.

Management Tools and Interfaces

Exchange Server SE offers several management tools and interfaces to simplify administration:

Exchange Admin Center (EAC): Exchange Server SE retains the modern web-based Exchange Admin Center that was introduced in Exchange 2013. This console is optimized for on-premises, online, and hybrid Exchange deployments.
Notification System: The EAC includes a notification viewer that displays information about expiring and expired certificates, the status of mailbox moves and migrations, and exporting mailbox content to .pst files. Administrators can opt to receive email notifications about these tasks.
Role-Based Access Control: Exchange Server SE continues to use role-based access control (RBAC) to determine and control each user’s administrator level while accessing the management console.
Unified Management Experience: For hybrid deployments, administrators can use centralized mailbox management through the on-premises EAC, providing a consistent management experience across both on-premises and cloud environments.
Exchange Toolbox Tools: Exchange Server SE continues to support Exchange Toolbox tools like Queue Viewer and Performance Monitor, though PowerShell scripts will need to be rewritten to use the new REST-based APIs once Remote PowerShell is deprecated.

Exchange Server SE represents Microsoft’s commitment to supporting on-premises email infrastructure while encouraging a gradual transition to cloud services. While not introducing a large number of new features, it focuses on improving security, reliability, and supportability for organizations that need to maintain on-premises Exchange deployments.

Integration with Microsoft 365 and Hybrid Deployments

Exchange Server SE continues Microsoft’s commitment to supporting hybrid deployments, providing organizations with flexible options to integrate on-premises infrastructure with cloud services. This integration capability is particularly valuable for organizations that need to maintain some on-premises presence while leveraging cloud benefits.

Hybrid Deployment Scenarios

Exchange Server SE supports several hybrid deployment scenarios to accommodate different organizational needs:

Full Hybrid Deployment: This configuration provides a seamless experience across on-premises and cloud environments, enabling features like shared address books, free/busy calendar sharing, and unified mail flow. It’s ideal for organizations gradually transitioning to the cloud or those that need to maintain some on-premises presence for compliance reasons.
Minimal Hybrid Deployment: For organizations primarily focused on mailbox migration to the cloud with less emphasis on feature integration, a minimal hybrid configuration provides the essential components needed for migration without implementing all hybrid features.
Regional Hybrid Deployment: Multinational organizations can implement region-specific hybrid configurations to address data residency requirements. For example, users in regions with strict data sovereignty regulations can remain on-premises while others migrate to Exchange Online.
Split Domain Hybrid: Organizations can maintain a shared domain namespace (e.g., @contoso.com) across both on-premises and cloud environments, allowing seamless communication while keeping certain mailboxes on-premises.

Integration with Microsoft 365 Services

Exchange Server SE integrates with various Microsoft 365 services to provide a cohesive experience:

Unified Global Address List (GAL): Users in both environments see a single address book, creating the appearance of a single organization regardless of where mailboxes are hosted.
Free/Busy Calendar Sharing: Calendar availability information is shared between on-premises and cloud users, enabling seamless scheduling across the organization.
Centralized Mail Flow: Organizations can configure all inbound and outbound Exchange Online messages to be routed through the on-premises Exchange organization, providing consistent mail flow policies and security controls.
Single Outlook on the Web URL: Users can access a unified Outlook on the web URL for both on-premises and Exchange Online mailboxes, simplifying the user experience.
Directory Synchronization: Azure AD Connect synchronizes on-premises Active Directory with Azure Active Directory, ensuring consistent user identities across both environments.
Message Tracking and MailTips: Administrators can track messages and leverage MailTips across the entire hybrid environment, improving troubleshooting capabilities and user experience.
Cloud-based Archiving: Exchange Online Archiving can be used with on-premises mailboxes, allowing organizations to leverage cloud storage for archiving while maintaining primary mailboxes on-premises.

Migration Paths to Cloud Services

Exchange Server SE facilitates several migration paths to cloud services:

Staged Migration: Organizations can gradually move mailboxes to Exchange Online based on user groups, departments, or other criteria. This approach minimizes disruption and allows for testing with smaller user groups before wider deployment.
Cutover Migration: Smaller organizations may opt for a complete migration to Exchange Online during a designated window, moving all mailboxes simultaneously.
Hybrid Migration: The most flexible approach allows organizations to move mailboxes between on-premises and cloud environments as needed, with the ability to move mailboxes back on-premises if required.
Mailbox Migration Tools: Exchange Server SE supports standard Exchange migration tools and PowerShell for coordinating larger, more complex migrations.

Long-term Coexistence Strategies

For organizations planning long-term hybrid deployments, Exchange Server SE supports several coexistence strategies:

Hybrid License Benefit: Microsoft provides a free Exchange Server license for hybrid deployments when certain conditions are met. Organizations with qualifying Microsoft 365 subscriptions (E1/E3/E5, Microsoft 365 E3/E5, Exchange Online Plan 1 or 2) can deploy Exchange Server for hybrid purposes without additional server licenses.
Hybrid License Restrictions: To qualify for the free hybrid license, the Exchange Server can only fulfill the CAS/cabinet and Hub role, cannot host any mailboxes (which should be in the cloud), and the organization must be a paying cloud customer with an Enterprise subscription.
Mail Flow Options: Organizations can choose between centralized mail routing (all mail flows through on-premises servers) or direct routing (mail flows directly to Exchange Online for cloud mailboxes), depending on their security and compliance requirements.
MX Record Configuration: For centralized routing, MX records should point to on-premises Exchange servers. For direct routing, MX records should point to Exchange Online Protection.
Hybrid Configuration Wizard: Exchange Server SE continues to support the Hybrid Configuration Wizard, which streamlines the setup process for hybrid deployments by configuring the necessary components and connections between on-premises Exchange and Exchange Online.
Server Requirements: Organizations implementing hybrid deployments should use the latest Cumulative Update (CU) or Security Update (SU) available for their version of Exchange. Microsoft recommends using Exchange Server with the latest CU and SU for configuring hybrid deployments.

The integration capabilities between Exchange Server SE and Microsoft 365 provide organizations with the flexibility to implement hybrid environments that meet their specific business requirements, whether as a transitional state during cloud migration or as a long-term solution for organizations with specific compliance or operational needs.

Maintenance and Updates

Exchange Server Subscription Edition (SE) introduces a more structured and predictable update model compared to previous versions, aligning more closely with Microsoft’s cloud services approach while maintaining the reliability needed for on-premises deployments.

Biannual Cumulative Updates (CUs)

Exchange Server SE follows a regular update cadence to ensure organizations can plan and prepare for changes:

Predictable Schedule: Microsoft will release two Cumulative Updates (CUs) per year for Exchange Server SE, providing a consistent and predictable update schedule.
Feature Enhancements: Each CU will include not only bug fixes and security updates but also potential new features and improvements, similar to the model used for Exchange Online.
Updates: CUs are packages containing all previous updates, meaning organizations can update directly to the latest CU without needing to install intermediate updates.
Testing Requirements: Despite the more predictable nature of these updates, organizations should still maintain proper testing environments to validate CUs before deploying to production servers.

Security Updates Delivery

Security remains a top priority for Exchange Server SE, with a structured approach to security updates:

Monthly Security Updates: In addition to biannual CUs, Microsoft will continue to release monthly security updates (SUs) for Exchange Server SE to address emerging threats and vulnerabilities.
Critical Security Patches: For particularly severe vulnerabilities, Microsoft will release out-of-band security updates as needed, which organizations should prioritize for immediate deployment.
Update Channels: Security updates will be delivered through standard Microsoft update channels, including Windows Update, Windows Server Update Services (WSUS), and Microsoft Update Catalog.
Subscription Requirement: Access to security updates requires an active subscription or Software Assurance (SA). If SA lapses, organizations lose access to Exchange Server SE updates, reverting to Exchange 2019 rights.

Patching Requirements and Best Practices

To maintain a secure and reliable Exchange environment, organizations should follow these patching best practices:

Regular Update Schedule: Establish a regular schedule for applying security updates, typically within 30 days of release for non-critical updates and within days for critical security patches.
Testing Protocol: Implement a structured testing process for all updates before deploying to production, including functionality testing for critical business processes.
Backup Strategy: Always perform full backups before applying updates to enable recovery if issues occur during the update process.
Staggered Deployment: For organizations with multiple Exchange servers, implement updates in a staggered approach rather than updating all servers simultaneously.
Health Verification: After applying updates, verify server health using Exchange health checks and monitoring tools to ensure all services are functioning properly.

Lifecycle Management Considerations

Exchange Server SE introduces a new lifecycle management approach that differs significantly from previous versions:

Modern Lifecycle Policy: Exchange Server SE follows Microsoft’s Modern Lifecycle Policy rather than the Fixed Lifecycle Policy used by previous versions. This means support continues as long as customers maintain their subscriptions and stay current with updates.
Minimum Notice Periods: Under the Modern Lifecycle Policy, Microsoft provides a minimum 30-day notification before required actions and 12 months to 3 years notice before end of support.
Update Requirements: Organizations must stay current with Exchange Server SE updates to maintain support. Microsoft typically requires customers to update to the latest CU or the previous CU to remain in a supported state.
Version Coexistence: Once Exchange Server SE CU1 is released (expected in late 2025), it will block coexistence with all previous Exchange versions, including Exchange 2016 and 2019. This creates a clear timeline for organizations to complete their migrations.
Subscription Management: Organizations must maintain active subscriptions or Software Assurance to retain access to Exchange Server SE. If subscriptions lapse, organizations lose access to Exchange Server SE and revert to Exchange 2019 rights.

Licensing Considerations for Enterprise Agreement Customers

Enterprise Agreement (EA) customers have specific considerations when planning for Exchange Server SE deployment, particularly those with existing Microsoft 365 investments.

Special Considerations for EA Customers with Microsoft 365 E3/E5

Enterprise Agreement customers with Microsoft 365 E3 or E5 subscriptions benefit from several special licensing provisions:

On-premises Server Rights: All Microsoft 365 Enterprise E3 and E5 User Subscription Licenses (SLs) purchased through an Enterprise Agreement include rights to install Exchange Server, SharePoint Server, and Skype for Business Server an unlimited number of times on servers dedicated to the customer’s use.
EA Savings: The Enterprise Agreement offers built-in savings ranging from 15 percent to 45 percent compared to other licensing programs, providing cost advantages for larger organizations deploying Exchange Server SE.
Payment Flexibility: EA customers have the option to spread out payments by making three annual payments instead of one up-front payment, helping reduce initial costs and forecast annual software budget requirements up to three years in advance.
True-up Process: During the term of an Enterprise Agreement, organizations can add and adjust users, devices, products, and services at any time without placing individual purchase orders, accounting for changes through an annual “true-up” process.

On-premises Exchange Licensing for Microsoft 365 Subscribers

Organizations with Microsoft 365 subscriptions have specific licensing options for Exchange Server SE:

Cloud Subscription Licensing Path: If all users and devices accessing on-premises Exchange Server SE have licenses with qualifying cloud subscriptions (such as Microsoft 365 E3 or E5), then Software Assurance is not required.
Hybrid License Benefit: Microsoft provides a free Exchange Server license for hybrid deployments when certain conditions are met. Organizations with qualifying Microsoft 365 subscriptions can deploy Exchange Server for hybrid purposes without additional server licenses.
Downgrade Rights: Microsoft 365 Enterprise E3 and E5 User SLs include downgrade rights for on-premises server products, allowing organizations to deploy previous versions of Exchange Server if needed.
Server Access Rights: Microsoft 365 E3 and E5 User SLs license users for access to Windows Server, but do NOT license the Windows Server product itself, which must be licensed separately.

Additional Costs and Requirements

Organizations should be aware of several additional costs and requirements when planning Exchange Server SE deployments:

Price Increases: Starting July 1, 2025, Microsoft will increase prices for its on-premises server products, including:

Standalone server licenses for Exchange Server SE will increase by 10%
Core CAL Suite will increase by 15%
Enterprise CAL Suite will increase by 20%

SQL Server Licensing: Organizations deploying Exchange Server SE must separately license any required supporting products, such as SQL Server.

CAL Restrictions: Users licensed with CALs acquired through a Volume Licensing agreement are not eligible to access servers licensed with the on-premises server rights included in Microsoft 365 E3/E5 subscriptions.

Opaque Pricing Structure: Microsoft maintains an opaque pricing structure for server licenses and CALs. Customers must work with Microsoft account teams or licensing partners for quotes, which many find frustrating. Budgeting often relies on extrapolating from previous costs plus the announced percentage increases.

License Management: Customers will manage software and product keys for Exchange Server SE via the Microsoft 365 admin center, which replaces the Volume Licensing Service Center.

These licensing considerations highlight the importance of carefully evaluating existing agreements and subscription status when planning Exchange Server SE deployments, particularly for Enterprise Agreement customers with Microsoft 365 investments.

Security and Compliance

Exchange Server Subscription Edition (SE) places a strong emphasis on security and compliance, building upon the foundation established in Exchange 2019 while introducing enhanced protections and integration capabilities with Microsoft’s broader security ecosystem.

Built-in Security Features

Exchange Server SE includes several built-in security features designed to protect against modern threats:

Windows Extended Protection: Exchange Server SE enables Windows Extended Protection by default during installation, enhancing authentication security by mitigating authentication relay and man-in-the-middle attacks through channel-binding information specified via Channel Binding Tokens (CBT).
TLS 1.2 as Default: Exchange Server SE continues Exchange 2019’s approach of enabling only TLS 1.2 by default, disabling support for older algorithms (DES, 3DES, RC2, RC4, and MD5) and configuring elliptic curve key exchange algorithms with priority over non-elliptic curve algorithms.
Server Core Support: Exchange Server SE fully supports installation on Windows Server Core, which Microsoft recommends as the preferred deployment option to reduce the attack surface and enhance security.
Block External Access to Administration Tools: Exchange Server SE allows organizations to use Client Access Rules to restrict administration of Exchange to internal networks only, eliminating the need for complex network and firewall rules.
Modern Authentication Support: Exchange Server SE supports OAuth 2.0 (Modern authentication) for pure on-premises environments using ADFS as a security token service (STS), enhancing authentication security.
Authentication Protocol Changes: Starting with CU1, Exchange Server SE will deprecate NTLM authentication in favor of Kerberos (Negotiate:Kerberos), aligning with modern authentication standards.

Compliance Capabilities

Exchange Server SE provides robust compliance capabilities to help organizations meet regulatory requirements:

Mailbox Audit Logging: Exchange Server SE supports mailbox audit logging, allowing organizations to track mailbox access and activities for compliance and security purposes.
Message Tracking: Enhanced message tracking capabilities help organizations monitor mail flow and investigate potential security or compliance issues.
Journaling: Exchange Server SE supports journaling capabilities for regulatory compliance, allowing organizations to capture and preserve email communications.
Retention Policies: Organizations can implement retention policies to ensure that email data is retained according to regulatory requirements and organizational policies.
Data Loss Prevention (DLP): Exchange Server SE includes DLP capabilities to help prevent sensitive information from being shared inappropriately.

Integration with Microsoft Sentinel

Microsoft Sentinel provides a powerful security information and event management (SIEM) solution that can significantly enhance Exchange Server SE protection:

Monitoring: Microsoft Sentinel enables centralized monitoring of Exchange Server SE environments, providing visibility into potential security threats and misconfigurations.
Threat Detection: Microsoft Sentinel includes built-in detection rules and analytics to identify potential threats to Exchange environments.
Incident Management: When threats are detected, Microsoft Sentinel creates incidents that security teams can investigate and remediate.
Exchange-Specific Solutions: Microsoft has published Exchange-specific solutions in the Sentinel content hub catalog to assist with detecting threats and misconfigurations in Exchange environments.

Setting Up Microsoft Sentinel for Exchange Environments

To protect Exchange Server SE with Microsoft Sentinel, organizations should follow these steps:

Create a Microsoft Sentinel Workspace: Begin by setting up a Microsoft Sentinel workspace in the Azure portal.
Install Required Solutions: From the Content Hub in Microsoft Sentinel, install the Exchange-related solutions, which include data connectors, workbooks, and analytics rules.
Deploy Azure Monitor Agent: Since Exchange on-premises does not have a native Sentinel data connector, organizations should leverage the Azure Monitor Agent (AMA) to collect and forward critical logs to the Sentinel workspace.
Configure Network Access: Ensure network access from on-premises Exchange servers to Azure (HTTPS: 443) to enable log forwarding.

Connecting Exchange Data Sources

Several key Exchange data sources should be connected to Microsoft Sentinel:

Windows Event Logs: Collect security logs (login attempts – Event ID 4624, 4625), application logs, and system logs from Exchange servers.
IIS Logs: Collect logs for services like OWA and EWS, typically located at C:\inetpub\logs\LogFiles.
Message Tracking Logs: Collect message tracking logs located at C:\Program Files\Microsoft\Exchange Server\V15\TransportRoles\Logs\MessageTracking.
Mailbox Audit Logs: Enable and collect mailbox audit logs for each mailbox to track access and activities.
Exchange Configuration Data: Collect data about Exchange configuration, including RBAC delegation, remote domain configuration, local administrator permissions, high privileged group members, and send/receive connector configuration.

Creating Custom Queries and Workbooks

Microsoft Sentinel provides powerful tools for analyzing Exchange data:

Custom Queries: Use Microsoft Sentinel’s query language (Kusto Query Language or KQL) to create custom queries that help monitor and detect suspicious activities within the Exchange environment.
Workbook Creation: Create custom workbooks to visualize Exchange data, making it easier to identify patterns and anomalies.
Workbook Templates: Microsoft Sentinel includes workbook templates specifically designed for Exchange environments, providing visualizations of Exchange security posture and activities.
Step-by-Step Process: To create a new workbook, navigate to the “Workbooks” section, select “Add workbook,” click “Edit,” incorporate text, queries, and parameters as needed, and save your modifications.

Configuring Alerts and Playbooks

Microsoft Sentinel enables automated alerting and response for Exchange environments:

Alert Configuration: Configure alerts based on custom queries to trigger when specific conditions are met, indicating potential security threats.
Playbook Creation: Create playbooks (automated response workflows) that can take actions based on the alerts triggered, such as sending notifications or initiating remediation steps.
Email Notifications: Configure playbooks to send email notifications when new incidents are created, ensuring timely response to potential threats.
Incident Assignment: Use automation rules to perform basic triage on new incidents and assign them to the proper personnel.

Monitoring and Investigating Incidents

Microsoft Sentinel provides tools for incident investigation:

Incident Navigation: Use the Incidents page to view basic information about all open incidents, including severity, status, and ownership.
Incident Filtering: Filter incidents by owner, status, severity, or product name to focus on relevant security events.
Incident Details: View detailed information about specific incidents, including affected entities, timeline, and related events.
Collaborative Investigation: Collaborate with team members to investigate and remediate security incidents affecting Exchange environments.
Threat Intelligence Integration: Integrate threat intelligence feeds to enrich Exchange data and help identify known malicious indicators.

By integrating Exchange Server SE with Microsoft Sentinel, organizations can significantly enhance their security posture, gaining visibility into potential threats and misconfigurations while enabling automated detection and response capabilities.

Summary

As we approach the release of Exchange Server Subscription Edition (SE) in the third quarter of 2025, it’s clear that this represents a significant milestone in the evolution of Microsoft’s on-premises email platform. Exchange Server SE marks not just another version update but a fundamental shift in Microsoft’s approach to on-premises server products.

Summary of Key Exchange Server SE Benefits

Exchange Server SE offers several notable benefits for organizations that need to maintain on-premises email infrastructure:

Simplified Upgrade Process: For organizations running Exchange 2019 CU14 or CU15, the in-place upgrade path offers a streamlined experience “identical to installing a CU,” making it substantially less complex than traditional Exchange Server version upgrades.
Continuous Updates: The subscription model ensures organizations always have access to the latest feature updates, security patches, and bug fixes as part of their subscription, eliminating the need to purchase new versions every few years.
Enhanced Security: Exchange Server SE includes significant security improvements, including Windows Extended Protection enabled by default, support for TLS 1.2, and the deprecation of less secure authentication methods like NTLM in favor of Kerberos.
Predictable Costs: The subscription model offers predictable annual costs, making it easier for organizations to budget for their IT infrastructure, particularly benefiting businesses that prefer operational expenditure (OpEx) over capital expenditure (CapEx).
Modern Lifecycle Policy: Unlike previous versions that followed the Fixed Lifecycle Policy with predetermined support dates, Exchange Server SE adopts the Modern Lifecycle Policy, providing more flexible support timeframes with minimum notice periods before required actions or end of support.

Recommendations for Different Organizational Scenarios

Different organizations will need different approaches to Exchange Server SE based on their current infrastructure and business requirements:

For Organizations Currently on Exchange 2019:

If already running Exchange 2019 CU14 or CU15, plan for the in-place upgrade to Exchange Server SE as soon as it becomes available
Ensure active Software Assurance or qualifying Microsoft 365 subscriptions to maintain licensing compliance
Begin testing authentication changes and identifying any scripts that rely on Remote PowerShell, as these will need updates after CU1

For Organizations on Exchange 2016:

With Exchange 2016 reaching end-of-support on October 14, 2025, there’s an urgent need to act quickly
Migrate to Exchange 2019 CU15 as soon as possible to establish eligibility for the in-place upgrade path to Exchange Server SE
The window between Exchange Server SE’s release (Q3 2025) and Exchange 2016’s end-of-support (October 2025) is extremely tight at just four months

For Organizations with Hybrid Deployments:

Leverage the free hybrid license for servers used exclusively for recipient management
Consider gradually transitioning more mailboxes to Exchange Online while maintaining the hybrid connection for management purposes
Ensure your hybrid configuration is up-to-date and compatible with Exchange Server SE

For Organizations Considering Cloud Migration:

Evaluate whether this transition point is the right time to consider moving to Exchange Online instead of investing in Exchange Server SE
According to Radicati Group research, Exchange Online already dominates with 84% of the global Exchange mailbox landscape, compared to just 16% for on-premises Exchange Server
Organizations with Microsoft 365 E3/E5 subscriptions may find the transition to Exchange Online more cost-effective than maintaining on-premises infrastructure

For organizations that must maintain on-premises email infrastructure due to regulatory requirements, data sovereignty concerns, or specific business needs, Exchange Server SE provides a path forward with modern licensing and security enhancements.

As we approach this significant transition in the Exchange Server lifecycle, organizations should carefully evaluate their options, considering not just the immediate licensing and upgrade requirements, but also their long-term collaboration and communication strategy in an increasingly cloud-centric world.

References and Additional Resources

To help organizations successfully plan, deploy, and manage Exchange Server Subscription Edition (SE), Microsoft provides a wealth of resources. The following collection of official documentation, community resources, training materials, and support options will be valuable for IT professionals working with Exchange Server SE.

Microsoft Documentation Links

Upgrading to Exchange Server SE: Microsoft has published detailed guidance on upgrading from current versions to Exchange Server SE, including licensing requirements and upgrade paths.

Exchange Server Documentation: Microsoft Learn hosts comprehensive documentation for Exchange Server, including the upcoming Exchange Server SE. This is the primary source for official guidance on planning, deployment, and management.

Exchange Server Supportability Matrix: This essential resource provides information on supported configurations and versions of Exchange Server, including operating system compatibility, coexistence scenarios, and supported builds.

Exchange Server Licensing Overview: Microsoft’s licensing page offers details about Exchange Server licensing options, including information about Standard and Enterprise server licenses and Client Access Licenses (CALs).

Exchange Server Roadmap: Microsoft has published the Exchange Server roadmap, which outlines the release schedule for Exchange Server SE and its cumulative updates.

Planning and Deployment Guide: This comprehensive guide helps organizations plan their Exchange Server deployment, covering prerequisites, architecture considerations, and implementation steps.