How can I transfer a cloud mailbox from user A to user B

Solution 1:

You were told correctly. It can't be done.

Here are four ways you can accomplish what you need:

  1. Disable the user account for UserA. Grant UserB Full Access to the mailbox for UserA.

  2. Convert the mailbox for UserA to a Shared mailbox. Grant UserB Full Access to the mailbox for UserA.

  3. Export the contents of the mailbox of UserA to a PST file. Import the PST file into the mailbox of UserB.

  4. Export the contents of the mailbox of UserA to a PST file. Attach the PST file to the email client of UserB.