strange error... any idea?

Youn Gonzales ispmgr at CLAS.NET
Wed Feb 13 23:57:43 GMT 2002

----- Original Message -----
From: "Miguel Koren O´ Brien de Lacy" <miguelk at KONSULTEX.COM.BR>
Sent: Wednesday, February 13, 2002 4:01 PM
Subject: Re: strange error... any idea?

> Another thing you may want to look at is if your installation requires a
> "reverse dns lookup" for accepting mails. I not sure though where in
> sendmail this is configured :-(  Of course it could also be that a
> is in place and blocking that ip? Check your end and their end of it. Ask
> them to do a "telnet your_ip 25" and see what comes up. Try this also to
> their ip and see what you get.

That feature is called accept_unqualified_senders and is configured in the file used to generate the file. Also of interest are
the accept_unresolvable_domains feature, access_db feature,
blacklist_recipients feature, and rbl feature. You can find more info on
these features at

I am by no means a sendmail guru, but you could probably modify the file and look for the error 550 - there should be several
instances. You could modify the wording on them so that you could tell which
of the rulesets were causing the reject. I believe there is also a way to do
this by running sendmail in test mode (sendmail -bt) and using check_mail.

from sendmail(8)
       -bt    Run in address test mode.  This mode reads addresses and shows
              steps in parsing; it is used for debugging configuration

Youn Gonzales
System Administrator
Comptia A+, Network+, INET+,
Cisco CCNA/CCDA Certified Technician
Microsoft Certified Professional

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