SMTP on 587

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jerryk
Posts: 3
Joined: Sun Jul 19, 2020 1:37 pm

SMTP on 587

Post by jerryk »

Hello,
Please excuse if this is a FAQ - but I have looked in many places and came up dry. Does anybody know - how can I get external mailservers to connect to my mailserver using port 587 instead of 25?

Background: I have sendmail running on my home Linux server. It has been connected to a DSL with static IP provided by Sonic.net for many years. The DSL died last week, and neither Sonic nor ATT have been able to get it back. I have ordered a Comcast Business line to replace it, but that's a week or so out.

In the meantime, to get *something* working, I attached a wifi station to the WAN port of the server, and got that to connect to my family's "entertainment" internet - which is supplied by Xfinity. And I set up port forwarding on the wifi router to put the server on the Internet, and modified the DNS records to point to the server's *current* IP address. Xfinity is dynamic IP, but it doesn't change unless you reboot the cable modem. A surprising amount of stuff now works, but....

....Xfinity blocks port 25, both directions. So no email. Pooey!

I bought a proper X509 certificate for the server, installed it, recompiled sendmail.cf with TLS support and started it up. Verified that
587 works with telnet. But still no mail is coming in. I bought a personal account with rollernet and set up mirroring so it snarfs my emails on their way to being rejected - because comcast is not passing 25.

How do I tell other servers to use 587 when they connect to my server? Is there maybe a DNS record for that? As far as I can tell, MX records don't do that; they just give IP addresses ( or FQDNs ).

Thanks in advance,

- Jerryk

Seth
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Joined: Sun Aug 30, 2009 10:44 pm
Location: Nevada
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Re: SMTP on 587

Post by Seth »

The short answer is you don't. Mail servers of the world expect port 25.

We have our SMTP Redirection service to accept mail, queue it, then send it to you on a different port when port 25 is blocked.
Seth Mattinen, Roller Network LLC

jerryk
Posts: 3
Joined: Sun Jul 19, 2020 1:37 pm

Re: SMTP on 587

Post by jerryk »

Seth wrote:
Sun Jul 19, 2020 2:03 pm
The short answer is you don't. Mail servers of the world expect port 25.

We have our SMTP Redirection service to accept mail, queue it, then send it to you on a different port when port 25 is blocked.
That sounds ideal. How do I activate it? Doesn't seem to be in the control panel.

jerryk
Posts: 3
Joined: Sun Jul 19, 2020 1:37 pm

Re: SMTP on 587

Post by jerryk »

OK, I got it working. A google search for "rollernet smtp redirection" got me to a help page with a link. Inbound mail is flowing on port 587!
Still challenged on the mail sending side though.

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