Exchange - Shared Mailbox Access (macmail)

Current May 2024

The documented procedure of signing in to a shared mailbox with an authorised user principal fails.

MacOS fails to display the option to sign-in as another user during the OAuth flow.

MacOS does not allow a username and password to be used to access more than one Exchange mailbox.

To access an Exchange shared mailbox from Mac Mail

IMPORTANT:

1. Safari Advanced tracking and fingerprinting must be disabled during the OAuth flow for the procedure to work.

Safari > Settings > Advanced

Disable Use advanced tracking and fingerprinting protection.

2. Assign a password to the shared mailbox

Microsoft 365 Admin portal > Active Users > Reset password.

3. In Apple Mail, add a new Exchange account using the shared mailbox address and password.