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Email to my organization (mycompany.com) goes through 2 sendmail servers running on CentOs 5.6, mail01 and mail02. I've configured a new sendmail server, mail03, in a different site for DR purposes, and am now testing it.

I haven't got the public MX records set up to point to the new server yet since that requires some red tape to get through, so I decided to test the new server internally. I started a telnet session from mail02 to mail03 port 25, and typed in the SMTP commands to send an email from gmail to me@mycompany.com. I receive the email, but I noticed that mail03 is relaying the mail to mail01 first, then mail01 delivers it to my internal exchange server. I have the mailertable feature enabled and a entry for mycompany.com that points directly to my exchange server, so I don't know why it would relay the mail somewhere else.

I couldn't find any configuration that would do that, so i thought it must be a DNS issue. Since I do not have the authority to change the public DNS records, I set up a test DNS server that contains an MX record for mycompany.com that points to mail03.

This time, sending a mail gets this error:

Dec 30 03:53:21 mail03 sendmail[1886]: rBU3qVcM001880: SYSERR(root): mail3.mycompany.com. config error: mail loops back to me (MX problem?)

Perhaps there is a setting that tells sendmail that its responsible for a domain or something? I don't remember having this problem when I set up the other 2 servers. Any help would be appreciated.

  • The server is not using the mailertable. Either the mailertable is wrong, or the configuration telling sendmail to use the mailertable is wrong. I can't say more than that without seeing the configuration. – Jenny D Dec 30 '13 at 10:52
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    You say "I have the mailertable feature enabled and a entry for mycompany.com that points directly to my exchange server"; please show us this, instead of just telling us. – MadHatter Dec 30 '13 at 10:53
  • Can you provide the contents of /etc/mail/access and /etc/mail/sendmail.mc? You might need to scrub them for private information but it would help to provide more context on the setup here. – Mike B Dec 30 '13 at 16:20
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As it turns out, it had nothing to do with sendmail's configuration. When I edited the resolv.conf file for the new server, I added in the nameserver entry, but did not edit the search domain entry, which was left as 'domain.org'. After changing that to 'mycompany.com', mail started relaying properly.

I don't know why this would make a difference though.

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