Unable to delete or archive mail Periodically, I keep getting an "x messages could not be moved to the mailbox xxx.  An error occurred while moving messages to mailbox xxx" popup (see below).  The only way I can resolve is to rebuild my entire mailbox, which takes a long time!  I am connected to an exchange server.  What is the likely cause of this issue?
I had the same problem and solved it successfully by rebuilding the mailbox (menu "Mailbox", then "Rebuild".