An error occurred while moving messages to mailbox “(null)” I just moved my IMAP email from one server to another and now while I'm trying to delete any emails, Mail produces the following error:


  An error occurred while moving messages to mailbox “(null)”.


I Google'd for it and found a lot of folks out there who are having the exact same issue but was not able to find solution.
Try selecting the Trash mailbox (folder) and then the menu item:

Mailbox → Use This Mailbox As → Trash Mailbox