Fix an IMAP path prefix problem with Mail

I have just switched hosts for my domain, including my email. My new host supports IMAP, where my old one did not, so I wanted to make the most of this to transfer all my mail folders to the server. I set up the account on my work MacBook Pro, and everything was fine. I made a directory on the server, then filled in that directory as the ‘IMAP Path Prefix’ in Mail’s preferences for the account, and I could successfully create mailboxes and move messages in.

When I set up the account on my MacBook at home, however, Mail was completely ignoring the IMAP Path Prefix I set, and insisted on listing the entire contents of my home directory, including all the invisible files (.bash_history and so on) and, even worse, the whole public_html tree where my Web site is stored. Looking at a trace of the IMAP communication between Mail and the server, it was clearly a problem on my local machine rather than an error on the server, because Mail was asking for mailbox listings without ment…