When some (large) email providers have more than one MX, it happens sometimes that one MX refuses SMTP connection incoming from my host while another one accepts it (for reasons unknown to me).

My question is if it's possible to ensure randomized (or round-robin?) selection of MX in a given domain in Exim on subsequent delivery attempts?

  • Your MTA is supposed to follow standards and follow the priority in MX records configured in the recipients DNS records. When multiple MX records of the same priority exist; those are supposed to handled in a round robin fashion. Round robin is a poor load balancer technique and simply will not guarantee that your next connection attempt will always go to a different server ... – HermanB Nov 15 '20 at 23:34

You can use the manual route to bypass the normal DNS routing that looks up MX records.

The manualroute router is so-called because it provides a way of manually routing an address according to its domain. It is mainly used when you want to route addresses to remote hosts according to your own rules, bypassing the normal DNS routing that looks up MX records. However, manualroute can also route to local transports, a facility that may be useful if you want to save messages for dial-in hosts in local files.


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