destination host is loopback

Kevin Miller Kevin_Miller at CI.JUNEAU.AK.US
Fri Aug 26 16:55:57 IST 2005

Joost Waversveld wrote:
>> I'm getting a number of errors everyday in my logs of the sort:
>> config error: mail loops back to me (MX problem?)
>> sure enough, if I do a DNS lookup for the above host, it resolves to
>> Is there anything I can do about this? I get about half a
>> dozen different hosts like this per relay per day.
> ----- Einde bericht van gmatt at NERC.AC.UK -----
> Are you using mailertable?? Then, be sure to put the
> hostnames/ipaddressess between [ and ] brackets... Otherwise sendmail
> will perform another MX lookup through DNS and will give you this
> error... 
> For Example:
> [root at bb ~]# cat /etc/mail/mailertable
> domain.tld         esmtp:[]
> domain2.tld        esmtp:[mail.domain2.tld]
> etc...

Not sure that's his problem.  If I'm reading it right, I think that's mail
from outside his system - probably NDR replies.

I had  a similar situation a couple years ago.  The spammer had
intentionally set their reply-to address to a domain that *they* resolved to so that they never had to bother with bounce messages and
complaints.  Sleaze bags.

My present solution is to reject any connections from that domain in
sendmail's access table.  At the time I wasn't running sendmail, and the
stupid program I was using just kept sending NRDs to itself, which weren't
accepted so it sent an NDR for the NDR, etc.  Didn't take long to fill up
the disk!  Thankfully sendmail is a bit smarter about it!


Kevin Miller                Registered Linux User No: 307357
CBJ MIS Dept.               Network Systems Admin., Mail Admin.
155 South Seward Street     ph: (907) 586-0242
Juneau, Alaska 99801        fax: (907 586-4500

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