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?
Google and MS are the entities you’d definitely want to keep your data away from, no thanks. And Proton doesn’t work with normal mail clients, which is kind of a dealbreaker. I remember seeing a comparison chart somewhere with an assortment of other services.