Sendmail error - mail loops back to me

[Timothy Czarnik]

We are getting some error messages from our Linux mail server (Red Hat 6.1) after a recent (this last weekend) rebuild. They are as follows:

553 mail.xxxxxxx.com. config error: mail loops back to me (MX
>problem?)
>554 ... Local configuration error

(Note that the x's replace actual server names and email address that are correct)

I have very little Linux experience, and I don't know sendmail very well. This server is delivering some of the mail correctly, but we are seeing these errors on a regular basis. Can anyone offer any suggestions?

Thanks in advance!
-Tim

[Dave Kelly_1 · Accepted solution]

You should check your DNS records first.

Run nslookup -query=mx and enter in the domain you are trying to send to.

You should get some output like this:

Server: nameserver.domain.com
Address: xxx.xxx.xxx.xxx

server1.domain.com preference = 50, mail exchanger = serverA.domain.com
server1.domain.com preference = 100, mail exchanger = serverB.domain.com
server1.domain.com preference = 110, mail exchanger = serverC.domain.com


This shows where mail for the domain you entered will be delivered. It does not mean that messages will terminate at these servers, it just means that these servers stand a better chance of knowing where to send your mail on. These entries are known as MX records (mail exchanger). The mail exchanger servers are tried in order of preference (lowest to highest) until the message can be delivered.

Check your MX records, it is possible that your DNS configuration is using your server as a mail exchanger and so is always trying to deliver outbound mail to it.


If this is not the case, check your sendmail.cf file for the DS macro. This is used to send all non-local mail to another machine for further delivery. It might be that this is set to point to your server.

[David Rodman]

There is one more place to look... In the Sendmail.cf file there is an option to check for
loops in the Helo command. The literal canonical name from the connecting host is
compared with the local canonical name (both systems have the exact same name)
a match will generate the error string you saw.

This might be normal under some circumstances. - Look for the F=k option
if F=k the check is skipped.
Happy hunting.

[Timothy Czarnik]

To all,

It was a combination of DNS and MX record problems. I thank everyone for their help!

-Tim

[Doug_24]

With sendmail and virtual hosting, there may be another area of problem. I have a main domain called foo.dom. I had an IP for mail.foo.dom. I have a virtual domain called bar.dom. I has an MX record for mail.bar.dom that is the same IP as mail.foo.dom. In this scenario sendmail needs to know to accept mail for bar.dom. In sendmail 8.12 there is a configuration directive for "local host names". Mine is set to a seperate file in the sendmail.cf with "Fw/etc/mail/local-host-names". So, I add bar.dom to that file name and all is well.

[Grogan]

I have to thank Doug for chiming in with his answer about the local-host-names file, long after the question was answered, and seemingly out of the blue. It led me to solving the problem, though the situation wasn't quite the same.

Much obliged to you folks for making this information available. (Google brought me to this)