Hello, I would like to contribute here and add a patch which in case of failed s2s connection digs the SRV records and tries on other port.
Can a dev working on OpenSMTPD please show me the logic and part and file on which I could add code on? Thanking you Sagar Acharya https://humaaraartha.in/selfdost/selfdost.html 10 Sept 2023, 15:40 by s...@spacehopper.org: > On 2023/09/09 13:49, Sagar Acharya wrote: > >> Thanks Peter, your comments were very helpful and I made some progress >> >> I have currently hosted server at 587. I have also set >> >> _submission._tcp.humaaraartha.in. SRV >> >> records which point to 587. However, I think such a thing is not implemented >> by default to be detected by mailservers, perhaps, SMTPD. >> >> Is such a check on other ports in case 25 connection is not established >> implemented? >> > > *nobody* does this. > > There was an opportunity to change how port lookups were done for email > when MTA-STS was implemented reasonably recently (it would only help for > the small number of senders actually using this, but it would still have > been something) - but that just continued to use port 25. > > If you think about the scope of changes that would be involved across > the internet, it's really just not possible to get everyone to change > this, so you would still need to list a port 25 receiver at least as a > backup MX (and honestly if you can do that, you might as well funnel > all mail through that machine). > > Changes like: > - everyone would need software that such a lookup > - some firewalls would need changing (it would be reasonable to only > permit an MTA to connect to random internet machines on ports needed > for email/DNS) > > I would suggest getting a VPS or hosted server somewhere, and either > bave that handle SMTP relay, or have a tunnel to your real mail server > so that incoming connections are passed across directly. >
