Hello. I am migrating from an ancient version of sendmail to a new machine using postfix on CentOS 7, and am having problems with what I thought would be the simplest of things - I've already started over multiple times (thank heavens for default config file backups!) but even walking one step at a time I keep stumbling. Doesn't help that there is frequently conflicting advice available from web searches. (Dovecot, on the other hand, seems to be working just peachie including STARTTLS using a Let's Encrypt certificate, so there's that.)
So I am asking if painfully newbie-ish questions regarding migrating from sendmail to postfix are permitted here. Been running linux a while, but sendmail was always a bit of a mystery, and postfix is brand-spankin'-new to me. Charlie Summers