Migrate mail from dovecot on centos to dovecot on debian I am trying to migrate a number of user mail accounts from dovecot 1.0.7 on a centos 5.11 server to dovecot 2.1.7 on a debian 7 server Foolishly I thought I could simply replicate the Maildirs from one server to the other using rsync, change the dns and all would be fine. Sadly that did not work. While the process did seem to go well Thunderbird on my test account is insisting on re downloading ALL the mail as duplicate unread emails. Is there a way I can import the mail from the source centos server to the destination debian server without forcing the user to potentially having to sort through and delete hundreds of duplicate emails? I am using IMAP for the mail protocol

I have solved the issue.

I have been meaning to do this move for a few months. in that time I have been rsyncing all users folders to the new server.

I forgot to add the --delete command to the rsync command thus old email messages were accumulating on the destination (new) server even after the user had deleted them from the old server.

Therefore when I switched to the new server dovecot automatically indexed the extra emails and the clients dutifully picked them up.