RE: DNS lookup for SMTP

It sounds like IBMi is operating correctly and MX takes priority over A for SMTP.

This came about because they changed all the DNS entries to a different IP. Things went terribly awry, so they changed some of the DNS entries back. They didn't change the MX because they thought it didn't matter.

Thanks



-----Original Message-----
From: David Gibbs via MIDRANGE-L [mailto:midrange-l@xxxxxxxxxxxxxxxxxx]
Sent: Wednesday, August 14, 2019 3:13 PM
To: Midrange Systems Technical Discussion <midrange-l@xxxxxxxxxxxxxxxxxx>
Cc: David Gibbs <david@xxxxxxxxxxxx>
Subject: Re: DNS lookup for SMTP

On Wed, Aug 14, 2019 at 3:07 PM Justin Taylor <JUSTIN@xxxxxxxxxxxxx> wrote:

Our Exchange admin changed the server IP today, and IBMi was no longer able to relay mail. My SMTP server has the hostname of the Exchange server. The Exchange admin says that IBMi is resolving the host name using the MX record in DNS instead of the A record in DNS. I have a Dick-and-Jane understanding of DNS, and I'd never heard of an MX record before today.

MX records for a domain indicate which fqdn (fully qualified domain
name) will accept mail for that domain (there can be more than one, part of the entry is the search priority).

If a mail server is trying to send mail to joe@xxxxxxxxxxx, it will look up the MX records for example.com. If will then try to connect to the host identified in the MX record. If it can't connect to the first one, it goes to the next highest priority record, until it has gone through all of them.

There must be an A record for each of the hosts identified in the MX records.

If there are no MX records for a domain, the "A" record for the domain will be used.

david

Can anyone shed some light on this? What record type should IBMi use? Is there a way to configure it?

TIA
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