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?
The domain won’t change that. Even with a static IP if it’s coming from an ISP owned up block you’re likely going to get banned. Even with reputable VPS’ it’s hard. Make sure you have DMARC, DKIM, and SPF setup, but even then almost certainly going to get banned. The big player are creating and inherent monopoly instead of improving their spam filters.