[Dshield] Odd sendmail log entries

Bob Poortinga bobp+dshield at webster.tsc.com
Fri May 6 14:37:49 GMT 2005

"David McGaughey" <mcgoy at plumbearcat.com> writes:
> I was checking my sendmail logs when I noticed a bunch of "loops back to me"
> errors.  Sure enough, a dig on one of the offending domains sending the
> e-mails resolves to  At almost exactly the same time there was
> another domain with errors in my logs that digs to  Is it just a
> misconfiguration or is there some sendmail rewrite rule exploit being
> tested?  Any information or experiences on this appreciated.

My experience is that spammers are registering domains to use when
sending spam that have MX records that look like this:

spamdomain.com  MX 10 localhost

Bob Poortinga  K9SQL
Bloomington, Indiana  US

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