Outlook Autodiscover Caching, MAC OS

Environment:

- Microsoft 365 tenant

- New Outlook for Mac

 - macOS Tahoe

Scenario:

An email address (email address removed for privacy reasons) previously existed as an alias on a

mailbox whose primary address was on Domain B (email address removed for privacy reasons).

Today, that alias was removed from the Domain B mailbox, and a new licensed

mailbox was created using the same SMTP address on Domain A

(email address removed for privacy reasons).

Behavior:

- Sign-in to the new mailbox works immediately in Outlook Web (OWA)

- Mailbox is accessible and functional online

- Adding the account in New Outlook for Mac fails with:

“This account has already been added”

- Account reset, sign-out, removal of all accounts, reinstall, and keychain

cleanup do not resolve the issue

Observation:

This appears to be related to Autodiscover or mailbox GUID caching in

New Outlook for Mac when an SMTP address previously existed as an alias on

a mailbox under a different primary domain.

Questions:

Is there any supported method to force New Outlook for Mac to re-resolve

the mailbox identity after alias removal?

Is this a known limitation or bug specific to New Outlook for Mac?

Additional note:

The issue occurs even though the mailbox is fully functional in OWA

immediately after alias removal and mailbox creation.