I'm trying to move my mail onto a different IMAP server. So I drag-and-dropped the mailbox. A while later, Mail seemed to be done.
However, the number of messages in the original mailbox is much larger than the number of mailboxes in the target mailbox. So I'm not sure if it successfully copied all the messages or not.
(However, the number of messages in the original mailbox *increased* subtantially after copying. The number of messages in the target appears to be the same as the number of messages in the original before copying.)
Is it safe to delete the original mailbox? Where are all these extra messages coming from? Why are Mail's mailbox counts so variable? I checked a few random messages, and they seemed all to have been copied, but there are thousands of messages and I don't want to find out later that some were lost. Is there any way of manually counting the number of messages in a mailbox to see if they are the same -- I don't trust Mail's counts (and no, I can't count past 1000 so I need software help

).
A second question: I also tried using Mail Scripts (found on the internet somewhere) to backup the folders, but it consistently ran out of memory. Any tips on how to back up my mail locally?