Postal as both SMTP server and incoming email relay

[rigobot]

Hello,

I configured Postal to act as SMTP server and incoming email relay at the same time for my domain mydomain.com. The server has hostname mail.mydomain.com which corresponds to the FQDN it's reachable to. Thanks to a routing entry, the incoming emails are sent to an SMTP endpoint (another host, say mail.otherdomain.com). All seems to work fine as long as I exchange mails between mydomain.com and another domain. In this scenario, I can send emails (to a domain != mydomain.com) as well as receive them (from a domain != mydomain.com). However, if I try to send emails to an address of mydomain.com, the message remains in the queue showing the following error:

Network is unreachable - connect(2) for "<IPv6 ADDR>" port 25, Connection refused - connect(2) for "127.0.0.1" port 25

I guess that Postal is trying to send the email to itself, instead of applying the forwarding rule.

As a disperate attempt, I tried to configure the array smtp_relays in postal.yml like so:

smtp_relays: [ 'smtp://mail.otherdomain.com:25' ]

Doing so, only the emails exchanged within the mydomain.com domain would work, but all the other emails that involved another domain would not.

Any hint on how to fix this problem is much appreciated! Thank you!

[willpower232]

Do any of your DNS records contain 127.0.0.1? I can't remember if it would get that value a different way...

[rigobot]

Yes, mail.mydomain.com is the localhost and resolves to 127.0.0.1. What happens should be along these lines:

• The remote email client (I'm using Outlook from Android) sends the email to [email protected]. The DNS records involved in SMTP all eventually points to mail.mydomain.com
• The email reaches correctly the queue in Postal (running in mail.mydomain.com).
• Postal processes the email and does not honor the forwarding rule that says "forwards the email TO [email protected] to mail.otherdomain.com)
• Instead, Postal tries to relay the email to the SMTP server of mydomain.com (which is itself).