Just a quick post to give warning to any beginners looking to set up Postfix. If setting up accounts to receive mail, go the extra mile and learn how to enable spam/virus filtering and reject backscatter-causing spam.
When I installed Postfix, the only thing actually needed was to send out mail. I wrote a script that emails me, and I also have logwatch email a daily report. It wasn’t necessary to enable incoming mail, but I did it for fun because I’d never set up a mail server before. Enabling incoming mail caused my server to send out undeliverable mail notifications in reply to spam. This has gotten me on two blacklists and has stopped Gmail from accepting any mails from my domain.
For now, I’m disabling the incoming mailbox and turning it into what is called a null client. I will also look into getting removed from the blacklist. First I’ll try this guide. My reports from logwatch are sorely missed because now I have to manually check the logs on my server.
Good luck on any of your email server endeavors and always keep security and spam in mind!