Microsoft is retiring EWS in 2026 — how to find every EWS call in your codebase

If your apps talk to Exchange Online over Exchange Web Services (EWS) , the clock is ticking. Microsoft is retiring EWS for Exchange Online, with blocking starting October 2026 . After that, EWS requests to Exchange Online stop working and you must use the Microsoft Graph API instead. (On-premises Exchange isn't affected the same way.) The migration itself is well documented. The annoying part is the first step: figuring out where your code actually touches EWS — especially in older or large codebases spread across .NET, Java, Python and PowerShell. Here's a practical checklist of what to look for, and what each maps to in Microsoft Graph. What EWS usage looks like Connection & auth Microsoft.Exchange.WebServices namespace, new ExchangeService(...) , ExchangeVersion AutodiscoverUrl(...) — Graph has no Autodiscover; use the fixed endpoint https://graph.microsoft.com/v1.0 WebCredentials / basic auth — replaced by OAuth2 via MSAL (delegated or app-only) exchangelib (Python), New-WebServiceProxy (PowerShell), microsoft.exchange.webservices (Java) Operations → Graph equivalents EWS Microsoft Graph FindItems / ItemView GET /me/messages ( $filter , $search ) EmailMessage + SendAndSaveCopy POST /me/sendMail FindFolders / WellKnownFolderName GET /me/mailFolders Appointment / CalendarFolder /me/events , /me/calendar GetUserAvailability POST /me/calendar/getSchedule ContactsFolder /me/contacts SyncFolderItems delta query GET /me/mailFolders/{id}/messages/delta StreamingSubscription (pull/push) Graph change notifications ( POST /subscriptions ) + webhook EWS impersonation ( ImpersonatedUserId ) app-only auth + target /users/{id} A faster way to scan Grepping by hand works, but it's easy to miss things. I built a small free tool for exactly this: EWScan . Drop in your project as a .zip (or individual files) and it lists every EWS reference — file, line, and the Microsoft Graph replacement for each — so you can scope the migration. It runs entirely in your browser; your source code is never uploaded. (Disclosure: I made it.) Migration tips Start with auth : set up MSAL + register an app in Entra ID, then port one read path (e.g. list messages) end-to-end before the rest. Prefer application permissions + /users/{id} where you used impersonation. Replace SyncFolderItems polling with delta queries , and EWS subscriptions with Graph change notifications . Don't wait until October — scan your code, scope the work, and migrate the high-traffic paths first.