Outgoing port 25 times out

[Arzumify]

I'm a hoster of a home email service, as I tend to stay away from the big email companies.

It's been running flawlessly for the last 6 or so months, but recently any connections I've tried to make to the server have timed out, but only on Port 25. Unfortunately, according to the SMTP specification, this is the only port that needs to be open.

As a result, could I find out a way to unblock port 25? It's not a port forwarding issue, as it's a recent change that only occurred in the past few weeks, and I've made sure port 25 is open.

[XRaySpeX]

Who is your email & domain provider?

[Arzumify]

I am my own email provider, like I said, and my domain provider is irrelevant, as the port is blocked regardless of DNS records

[XRaySpeX]

& It's you that running on your EE's router's LAN the SMTP server listening on port 25?

[Arzumify]

Yes. Both Port 80 and 443 work from the same server and port forwarding configuration.

[XRaySpeX]

When an email provider's network is not the same as the user's network the user is usually prevented from using the unauthenticated SMTP Port 25 for that very reason. I presume that check is done in the SMTP. Could yours be doing that?

Consequently most providers provided instead an authenticated SMTP on Port 465 or 587. Could you try that instead?

[Arzumify]

You misunderstand. To connect to a SMTP server from your computer, you indeed do not use port 25, but instead the submission port, usually 587. However, server-server SMTP **must** be over port 25, but may use STARTTLS to upgrade to an encrypted connection.

[XRaySpeX]

OIC! I never understood it was "server-server SMTP" but took it to be the normal, common, everyday, run-of-the mill user-server SMTP.

So I was trying to remember my half-remembered fact of the only peculiarity of port 25 SMTP that I wot of!