Help I seem to have screwed up my Postfix config

How do you get back to a baseline stock Postfix config? ServerAdmin seems to take settings from some place other than main.cf. I copied /etc/postfix/main.cf.default back in place, removed /etc/MailServicesOther.plist, rebooted and got back into SA. It looked like a clean config. So I went about setting it up the way it used to be using the SA gui and it still doesn't work. I enable SMTP and POP and IMAP and although the settings are checked, the services just don't start. When I run postfix -v -v from the command line, I get: postfix: dict_update: mydomain_fallback = postfix: fatal: bad string length 0