Re: Check for blacklists
While some organisations block dynamic ips, not all do. Sendmail (what I use, so I know this works) allows you to change the routing based on the email address you're sending to. So most mail goes direct, and where the recipient domain is blocking a dynamic ip address, the mail gets sent via another mail server. Could be your ISP, although I use the server for another domain I have which includes mail hosting. The return address is still set to my own domain so (Hotmail is one example, IIRC) mail to Hotmail goes via<other domain server> and replies come directly back to my server.
Every now and then I get another email blocked, so I add the domain to the routing list. I think I have about a dozen or so in the table now, after getting on for 20 years of running my own server.
I've never looked at PostFix, so I'll be following this series with interest. Dovecot, Spamassassin and fetchmail I know.