Server with assp and smarthost: bounces from smarthost get error refused to talk to me: 451 4.7.1

abkrim asked:

I’ve a sever centos 7 with Exim and ASSP
Some times, I need outgoing mail using another server how smart relay.

If smart server (running postfix) get a error (bounces, return one forbidden from remote server destination of one email,…) server smart can communicate with my server Centos.

host domain_of_my_centos_host [176.XX.XX.205] refused to talk to me: 451 4.7.1 Please try again later

I am trying to find the means of eviatr this, or to know if it is an error of my configuration.

My answer:

The extended status code tells me that the remote SMTP server is refusing the email you are trying to send. The error message doesn’t say why, though.

RFC 3463 tells me about X.7.1:

      X.7.1   Delivery not authorized, message refused

         The sender is not authorized to send to the destination.  This
         can be the result of per-host or per-recipient filtering.  This
         memo does not discuss the merits of any such filtering, but
         provides a mechanism to report such.  This is useful only as a
         permanent error.

Since it was returned as a temporary error rather than a permanent error, something else must be going on.

A quick search of the Internet indicates that several mail server addons can return this when they encounter a problem. In particular this seems to occur when the tool mimedefang has an error, timeout, or other problem. Thus any other product that uses mimedefang internally also will report the error if it has a problem. Some examples include anti-virus, greylisting, etc.

This is not a problem you can solve on your end. But it is something you should report to the postmaster of the smarthost. They may not be aware that they are having a problem with their incoming mail.

View the full question and any other answers on Server Fault.

Creative Commons License
This work is licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License.