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Transend’s Microsoft Graph Readiness

Microsoft’s retirement of Exchange Web Services (EWS) and transition to the Graph API is changing how migration platforms access Exchange Online.

Transend already supports Microsoft Graph in Transend Migration Console v3.2, with fully functional Graph-based migrations available today. Transend will continue to support both EWS and Microsoft Graph through the final EWS sunset, giving customers flexibility to select the protocol best suited to their migration.

Our Graph readiness extends beyond development and testing. Transend is already using Graph in production across our fully managed migration services projects, successfully migrating customer data to and from Microsoft 365 with Graph. This proven experience helps reduce risk, protect project timelines, and ensure customers are prepared for the transition from EWS to Graph.

Rather than waiting for an EWS-dependent migration vendor to catch up, Transend customers can move forward today with proven Graph technology and an experienced migration team.

What is changing

EWS disablement begins globally in October 2026, and Microsoft currently plans to fully disable EWS in April 2027. The phased process and administrator controls mean that October 2026 is the start of disablement, but not a single universal shutdown date. Microsoft recommends that organizations inventory active EWS applications and begin moving them to Graph now. This retirement concerns only Exchange Online as Graph is not supported for on-premises Exchange Server mailbox access.

Why migration vendor readiness matters

Migration tools may rely on EWS to read a Microsoft 365 source mailbox or write to a Microsoft 365 target mailbox. This affects tenant-to-tenant migrations and cross-platform projects moving into or out of Microsoft 365. A customer that has not implemented and tested a Graph migration path may have to delay a cutover, rely on temporary EWS availability, narrow the supported scope, or change tools late in the project. These are planning risks that are easily eliminated by choosing a migration vendor who properly supports the Graph API.

How Transend is prepared

While some migration vendors may be able to say, “We support Graph,” Transend can make a stronger statement: “We are already successfully using Microsoft Graph in production.”

Transend Migration Console v3.2 includes Microsoft Graph as an optional API selection that is fully functional, while labeling the protocol Preview as functionality and interface details continue to be optimized. This gives Transend a usable Graph path now and allows a project team to choose and validate it before production. Transend has also documented an approach to combat current Graph API limitations (i.e. see below “Calendar invitation storm”).

Additionally, Transend’s readiness for Microsoft Graph goes well beyond development and lab testing. Transend is already using Microsoft Graph in production across its fully managed migration services engagements, successfully migrating customer data to and from Microsoft 365 using Graph-based connectivity.

This hands-on production experience provides Transend with a significant advantage as Microsoft transitions away from EWS. Our migration technology, engineering teams, and service delivery processes have already been exercised against Graph in real-world customer environments, allowing us to identify and address the practical considerations that may only become apparent during production migrations.

For organizations planning Microsoft 365 migrations, a vendor’s readiness for Graph is increasingly critical. Selecting a migration provider that has not yet proven its Graph capabilities in production can introduce unnecessary technical risk as EWS approaches retirement. Transend customers can move forward with confidence knowing that our Microsoft Graph migration capabilities are not simply part of a future roadmap, but are already being used successfully in production today.

Managing Graph-specific considerations

Scope considerations

Graph introduces additional migration scope and permission considerations. To simplify the setup of the application used for authentication, Transend provides the m365_initialize_app.ps1 PowerShell script through TMCTools. This app initializer programmatically creates the Microsoft Entra ID app registration and service principal, assigns the Microsoft Graph, Exchange, and SharePoint permissions used by the migration tools, grants admin consent, creates a client secret, and assigns the required directory role. This reduces manual configuration and helps establish the access needed for migration.

Calendar invitation storm

Due to a current limitation with the Graph API, Microsoft 365 may automatically send unwanted meeting invitations or updates to attendees (“invitation storm”) as calendar events are migrated into Microsoft 365. To mitigate this unwanted invitation storm, Transend guidance provides a recommended setting in TMC and an alternative Exchange Online mail-flow approach.

To avoid this unwanted invitation storm when Graph is the target, we recommend one of two proven methods:

  1. Enable custom option /D207 in TMC when Graph is the target, which removes attendees from the event header and places them in the event body, preventing unintended notifications.

  2. Transend documentation provides guidance and free tools to enable temporary Exchange Online transport rules to suppress these messages during migration. Rules require careful setup, a controlled window, verification that legitimate mail is not suppressed, and removal after migration.

Best practices

When Transend delivers a migration as a managed service, we follow a proven, thoroughly tested methodology designed to minimize risk and deliver predictable results. Based on that experience, we recommend the following best practices to help ensure a successful migration.

  • Inventory source and target mailbox types, archives, public folders, group mailboxes, calendars, and on-premises components. Identify where EWS is used today.
  • Confirm the TMC version and API choice for each endpoint, required Graph permissions, tenant policies, and access to representative test accounts.
  • Perform pilot testing with mail, calendars, contacts, tasks, large folders, recurring meetings, attendee-heavy events, and any special mailbox types in scope.
  • Choose and test calendar notification handling before the first production pass. Record the tradeoff of attendee removal versus transport-rule suppression.
  • Keep the validated protocol unchanged throughout production. Do not switch between EWS and Graph after production migration begins, including during delta passes or cutover. Select and validate the protocol during setup and pilot testing so production uses a consistent, tested configuration.
  • Confirm data fidelity at source and target, document exceptions, and repeat delta and cutover tests at expected scale.
  • Recheck Microsoft’s roadmap and Transend’s release documentation before promising archive, public-folder, group-mailbox, or sovereign-cloud support.

Technical documentation

Microsoft Graph APIs are generally available for Exchange Online primary and shared mailboxes. Its initial GA release excluded archives, public folders, and Microsoft 365 Group mailboxes, while Microsoft’s roadmap targets import and export for those types in Q4 2026. Graph also does not replace mailbox access to on-premises Exchange Server.

The following tech notes provide more in-depth information about Microsoft Graph considerations, feature support, and API limitations.