Backing up and Importing IMAP folders

I am running Dovecot with Postfix on a FreeBSD machine. There are problems with the drive and I cannot depend on it. Dovecot saves all mail in IMAP format. I want to back up the mail folders, install a new HD, install the latest FreeBSD OS and then reinstall my programs. Reinstalling Dovecot is simple, but how do I reinstall the IMAP folders? Can Dovecot backup the folders onto a CD and then import them when I reinstall it? My mail is kept under “/var/mail/vmail”. Should I just back up that entire directory structure and then restore it later?

Thanks!

-- Jerry