Outbound Mail Not Sending – Port 25 Blocked? Need Guidance

Hey folks,

I’ve been running a small personal mail server for learning purposes — mostly to understand how mail flows and to get better at server administration. So far, everything’s been a great experience and a solid challenge.

Here’s the issue I’m stuck on:

I can receive emails just fine.

But outgoing emails aren’t leaving the server.

Looking into it, I suspect outbound port 25 might be blocked by digitalOcean or something upstream.

I ran nc -v smtp.domain.com 25 test and it just hangs — which suggests some filtering is in place.

So my questions are:

Is there a safe and legitimate way to get outbound port 25 unblocked, or a recommended alternative approach?

Should I be asking my hosting provider, or is it better to just route through a smarthost (e.g., via port 587)?

What would you do if you wanted to fully understand the end-to-end of sending mail from your own box without relying on a third-party relay?

I want to be respectful of best practices and avoid getting flagged, but also curious enough to want to know how it all really works under the hood.

Any advice or pointers would mean a lot — especially from those who’ve gone down this self-hosted rabbit hole. Thanks in advance for reading.