Mail Getting Rejected When Having a Mix of Good and Bad MX Records (Doc ID 1900345.1)

Last updated on JUNE 21, 2017

Applies to:

Oracle Communications Messaging Server - Version 7.0.0 and later
Information in this document applies to any platform.

Symptoms


A messaging server needs to send mail to another messaging server, serving another separate mail domain.

This external domain has 4 MX records in DNS, but was badly configured :

domain.com.    IN      A       <valid ip address>
domain.com.    IN      MX      100     invalid1.domain.com.
domain.com.    IN      MX      100     valid1.domain.com.
domain.com.    IN      MX      200     invalid2.domain.com.
domain.com.    IN      MX      200     valid2.domain.com.

The hosts invalid1 and invalid2 were as the name suggests invalid entries, invalid as in : not resolvable,
the hosts behind the valid1 and valid2 names were resolvable but for other reasons the hosts were rejecting connections.

At the moment the issue happened, we were unaware there was an error with the MX records.

In the mail.log file we noticed mail was being rejected, with an R action code :

where <IP of valid1.domain.com> contained the IP address of the host valid1.domain.com.

Why was mail being rejected and not simply queued as at least two of the MX names were resolvable ?

Also, the rejection reason seems to be 'Illegal host/domain name found', but further down the line there is a contradiction to this by showing the IP address of one of the valid MX servers.
Is this string maybe a left-over from a previous attempt, or overwritten by something else ?

 

Cause

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