[Mailman-Users] virtual host problem - mail not originatingfromsubdomain

David Buntin dbuntin at gvtc.com
Tue Aug 21 22:01:08 CEST 2007

>Alternatively, you could have sendmail send the message to something 
>like "tee" so that the full contents of the message(s) can be saved 
>to a file somewhere, prior to their being handed to Mailman.

OK. I modified my aliases file to pipe email to tee before it goes to
Mailman. (The line in the aliases file reads: mailman: "|tee /tmp/email-log
|/home/user/mailman/mail/mailman post list2") This works great and confirms
our suspicion. The log clearly reveals that the "To" field in the email is
replaced before it is delivered to Mailman. With a little more
investigation, I found that a neighboring MTA is replacing the "To" field
before it even gets to my server. As the mail RFCs require, the MTA is
expanding the CNAME alias subdomain.domain.com with the MX record of
domain.com. Mailman allows this "To" field with the missing subdomain to
pass through unmodified and forwards it to the mailing list. This gives the
appearance that Mailman is omitting the subdomain from the "To" field.

>Use an A record.  Even if it is exactly the same A record you use for 
>other machines.  It will work.  Trust me.

I deleted the DNS CNAME record and created a DNS A record for
subdomain.domain.com with a parameter equal to the IP address of my server
(the same address as domain.com.) This did not work at first. I found that
all email to subdomain.domain.com was rejected by my incoming MTA (sendmail)
with an error "config error: mail loops back to me (MX problem?) 554 5.3.5
Local configuration error"

This was the result of a sendmail configuration error. Sendmail was not
aware that it should service mail addressed to subdomain.domain.com. Now
that the CNAME record was gone and the neighboring MTA wasn't replacing
subdomain.domain.com with domain.com, sendmail on my server was no longer
able to receive mail originally sent to subdomain.domain.com.

To solve the problem, I made a change to my /etc/mail/sendmail.cw and added
subdomain.domain.com to the list. This change made sendmail accept email to
subdomain.domain.com. (This is the solution for my server running sendmail
on Red Hat Enterprise 2. I'm sure there is a similar setting for other

Now it all works well.

Sorry for the long explanation. I wanted the resolution to be documented for
any others who may find and read this in the archives.

Mark/Brad, thank you for your dedication and willingness to help out the
inexperienced. I very much appreciate your efforts.

David Buntin

More information about the Mailman-Users mailing list