Microsoft has issued a final retirement notice for legacy basic authentication in Exchange Online. Tenants still using basic auth protocols will be fully blocked starting March 31, 2026.
Action required before March 31, 2026.
What You Need to Do
- Audit connectors in the Exchange Admin Center
- Migrate to Modern Authentication
- Review third-party app dependencies
Use the Auth Policies section in the Exchange Admin Center to identify and update any remaining basic auth connections.
Our Take
This is the right call, but Microsoft is underselling how disruptive it'll be. Users have built years of muscle memory around that Chat / Teams split — expect a wave of support tickets the week it lands. Get ahead of it with a quick communication to your users before it shows up, not after.
Bottom Line
Good change, bad rollout timing for unprepared orgs. Send a user comm now.
