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?
You should be aware that a large number of mail hosters will block all mail from your server merely because it is sent from a dynamic IP address.
I’ve got a domain
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.
If you manage to get a good SMTP relay host or authenticated SMTP account for your outgoing email then playing around with small scale self hosting email (Granted that it is not your important daily driver email accounts) can be an interesting and fun experience. But you will have to invest some time reading and tweaking and figuring things out. Slightly comparable with installing Arch Linux. Lots of people will warn you to not do it but you might learn a few valuable things on the way there.
Meh that sucks i even have a perfectly working ddns, I mean I know I don’t get something like a PTR record but i wish that mail hosters would allow for more self hosting options