Shared Outlook account

Add the shared mailbox as an account in new Outlook so its category list remains available instead of accessing it only as a shared folder.

Add the shared mailbox as an account

This requires Full Access permission to the shared mailbox.

1. In new Outlook, open Settings → Accounts → Shared with me.
   Alternatively, select File → Account info.
2. Expand the shared mailbox.
3. Select Convert to add an automatically mapped mailbox as an account.
   • If it was not automatically added, select + Add and follow the prompts.
4. Open Settings → Accounts → Your accounts.
5. Confirm that the shared mailbox appears there as a separate account.
6. Open the category settings and select the shared mailbox from the account selector. Create and manage the categories under that mailbox rather than under your personal account.

Adding the mailbox as an account exposes its own Categories, Rules, Notifications, and Automatic Replies settings in new Outlook.^1^

If Convert or Add is unavailable

Ask your Microsoft 365 administrator to grant your account Full Access to the shared mailbox. Restart new Outlook after the permission has taken effect, then repeat the steps above.

The option to add a shared mailbox as an account might not yet be available in every new Outlook version. If the mailbox does not appear under Your accounts, either the necessary permission is missing or that feature is unavailable in the installed version.^1^

If the categories still turn grey

1. Open the shared mailbox in Outlook on the web and assign a category to a test message.
2. If it works there, return to new Outlook and go to Settings → Accounts → Shared with me.
3. Remove the affected shared mailbox, close Outlook completely, reopen it, and add the mailbox again.
4. Allow several minutes for synchronization before testing.
5. If necessary, create a temporary category in the shared mailbox through Outlook on the web, then reopen new Outlook. This can refresh the shared mailbox’s category metadata.^2^

If categories also cannot be assigned in Outlook on the web, have the administrator review mailbox access rather than reinstalling Outlook. Category operations in another mailbox depend on the permissions granted for that mailbox and its folders.^3^

If the problem continues after the mailbox is shown under Your accounts with Full Access, the Microsoft 365 administrator should open Microsoft 365 Admin Center → Support → Help & Support and include the shared-mailbox address, affected users, new Outlook version, and whether Outlook on the web works.

References

1. Manage shared mailbox settings in new Outlook | Microsoft Support
2. Outlook Shared Inbox will no longer let me categorize our emails. my teammates still can but I can no longer as it is now greyed out. - Microsoft Q&A
3. You cannot change a user's categories when you work as a delegate in Outlook | Microsoft Support