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?
Many ISPs will also block inbound SMTP unless you have business account (and sometimes even then) because it’s a common malware/spam vector.
If you insist on going through with this the key thing is to make sure that you’re not an open relay.