In Mac mail I have most of my email accounts set up Hotmail, Gmail, Yahoo, and Exchange (office365 hosted). When I try to move any of my messages from the first 3 (all IMAP accounts) into my Exchange ...
In our case the Apple Mail client stops retrieving new incoming e-mail messages. Rebuilding the mailbox doesn't improve. After looking at the "Mail Connection Assistent" a.k.a. "Mail Connection ...