WorkMail IMAP Login Fails for Shared Mailbox Despite Full Access Permissions

Amazon WorkMail does not support IMAP access to shared mailboxes directly using another user's credentials—even if that user has Full Access or Send on Behalf permissions, I thought it was because IMAP will be failed since it requires direct authentication to the mailbox, which shared mailboxes do not support in the same way, below some workarounds to consider:

1. Convert Shared Mailbox to Regular User Mailbox If IMAP access is essential, consider converting the shared mailbox (B@domain) into a regular user mailbox. This allows direct login and IMAP access using its own credentials.

2. Use Webmail or Outlook with Delegation Since user A@domain can access B@domain via the WorkMail web interface, you can:

• Use Outlook with WorkMail integration, which supports delegated access to shared mailboxes.
• Avoid IMAP and use Exchange Web Services (EWS) or ActiveSync, which support delegation better.

3. Use AWS WorkMail APIs If automation is the goal, consider using the Amazon WorkMail Message Flow API to programmatically access mailbox content.

Hey,

Hope you're keeping well.

IMAP in Amazon WorkMail only supports direct login to the mailbox that owns the credentials, so you can’t connect to a shared mailbox using your own account’s username and password. Full Access permissions let you open the shared mailbox in the WorkMail web app or Outlook, but they don’t extend to IMAP authentication. To use IMAP, the shared mailbox needs its own WorkMail-enabled user with a password set, and you’d connect using that mailbox’s credentials. You can create this in the WorkMail console under Organizations > Mailboxes > Create user, then assign the address and enable IMAP in the user settings.

Thanks and regards,
Taz