I have a raspberry pi running postfix. I Realised unless I open port 25 I absolutely cannot receive emails (I have 587 open and can send but not receive them). However I heard there are scaries online which someone could potentially send emails from your server without consent. I believe as well my ISP doesn’t block port 25. Is there anything I should do right now before opening port 25, or should everything be safe enough?
Have you ensured that your setup will pass email authentication processes?
It has been a long time since email from random hosts is accepted for forwarding or delivery. This Wikipedia may help https://en.wikipedia.org/wiki/Email_authentication