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?
Avoid being an open relay indeed. Some background information : https://www.postfix.org/SMTPD_ACCESS_README.html#relay But with the defaults in postfix you should be fine unless you made a lot of changes and made a mistake in it.