> On Apr 22, 2021, at 13:01, ED Fochler <[email protected]> wrote: > > No. > > You're only trying to send mail. Your ISP is only trying to stop you from > sending mail. > > Mail delivery is meant to be very well defined and easy to identify. If your > ISP is blocking connections to port 25 then they are blocking all mail, spam > and otherwise. The solution is to set up a mail server on a network that > allows mail. This can be a $5/mo cloud server. You can then 'submit' mail > to your mail server using other ports, but the mail server will talk to other > mail servers on standard ports, primarily port 25.
So, I actually have this same problem. I do have a VPS, which is my mail server (and have no problems sending mail, such as this one, using my MUA to connect to the VPS-based MTA). I have about 8 little PCEngines Alix and APU devices, all sitting at home, with an ISP that blocks port 25 (and lord do I wish I had the option for another ISP). They all run OpenBSD/OpenSMTP. The problem I’ve run into is I’m not sure how to use the submission port to “submit” mail to my mail server. Since I have the cron emails being sent, how do I get those routed to the VPS? How do I get basically all the emails for a couple of users forwarded to the VPS without, you know, relaying mail? Do I set up an account on the VPS, and tell SMTPD to relay all mail to my domain to that submission port? That sounds like relaying, and, as stated elsewhere in this thread, "Emails must be relayed on port 25.” Back in the before-times, I used sendmail’s concept of a smarthost, and just pointed it at that host, and could also tell it what port to connect on. I’m fine with “you can’t relay on any port other than 25”, but then how do I get the mails the system generates to my mailserver running on the VPS? Frankly, I think it’s kinda an odd restriction that you MUST use port 25 to relay mail between hosts if you own both hosts. If I want to use port 2525, I should be able to the one MTA to relay to the other MTA on this IP:port combination. I get that OpenSMTPD doesn’t have this ability, but I don’t see what this breaks if it’s allowed. Sean PS I’ve debated just setting up matching pf rules that accept connections on the internal side on port 25 and route-to the mail server on port 2525, and on the mail server taking connections on port 2525 and sending it to port 25. . . seems like unnecessary pf gymnastics (if it would even work).
