http://intrcxv4fa72e5ovler5dpfwsiyuo34tkcwfy5snzstxkhec75okowqd.onion/blog/email-service
Daring, aren't we? Dovecot was by far the most annoying to configure, and the best advice I can give is to read through all the config files and to adjust as you see fit. Email is probably the bulkiest and most annoying service to set up, and unless you're going for a configuration with multiple users like I did, you're best off just following the LandChad tutorial.