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Old 09-08-2009, 08:46 PM   #1
hitcttd
LQ Newbie
 
Registered: Sep 2009
Posts: 2

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Sendmail: 550: User Unknown erros


Hello,
I'm running into issues with sendmail. It seems likei I'm able to send mail to just about every domain except for ONE. Basically here is what i've figured out:

When i send mail to this particular domain, the box for some reason thinks that it's the mail handler and returns "user unknown" instantly.


i'm running sendmail -v -t -i user@dumbdomain.com

and right away i get "user unknown"

I've checked DNS configurations for the domain in question, all records look good. I've confirmed that i didn't have any funny aliases set up and have also confirmed that local-host-names is empty.

I can send mail to every domain i can think of except this one.

The box is webserver running your typical AMP applications.

Thanks for the help guys!

hello
test@DUMBDOMAIN.com... Connecting to [127.0.0.1] via relay...
220 NAME.host.MYSERVER.net ESMTP Sendmail 8.13.8+Sun/8.13.8; Tue, 8 Sep 2009 15:46:53 -1000 (HST)
>>> EHLO NAME.host.MYSERVER.net
250-NAME.host.MYSERVER.net Hello localhost [127.0.0.1], pleased to meet you
250-ENHANCEDSTATUSCODES
250-PIPELINING
250-EXPN
250-VERB
250-8BITMIME
250-SIZE
250-DSN
250-ETRN
250-DELIVERBY
250 HELP
>>> VERB
250 2.0.0 Verbose mode
>>> MAIL From:<USER@NAME.host.MYSERVER.net> SIZE=6
250 2.1.0 <USER@NAME.host.MYSERVER.net>... Sender ok
>>> RCPT To:<test@DUMBDOMAIN.com>
>>> DATA
550 5.1.1 <test@DUMBDOMAIN.com>... User unknown
503 5.0.0 Need RCPT (recipient)
>>> RSET
250 2.0.0 Reset state
>>> RSET
250 2.0.0 Reset state
thanh... Using cached ESMTP connection to [127.0.0.1] via relay...
>>> MAIL From:<> SIZE=1030
250 2.1.0 <>... Sender ok
>>> RCPT To:<USER@NAME.host.MYSERVER.net>
>>> DATA
250 2.1.5 <USER@NAME.host.MYSERVER.net>... Recipient ok
354 Enter mail, end with "." on a line by itself
>>> .
050 <thanh@NAME.host.MYSERVER.net>... Connecting to local...
050 220 NAME LMTP ready
050 >>> LHLO NAME.host.MYSERVER.net
050 250-ws21
050 250-8BITMIME
050 250-ENHANCEDSTATUSCODES
050 250 PIPELINING
050 >>> MAIL From:<>
050 250 2.5.0 ok
050 >>> RCPT To:<USER>
050 >>> DATA
050 250 2.1.5 ok
050 354 go ahead
050 >>> .
050 250 2.1.5 thanh OK
050 <USER@NAME.host.MYSERVER.net>... Sent
250 2.0.0 n891krUH006694 Message accepted for delivery
thanh... Sent (n891krUH006694 Message accepted for delivery)
Closing connection to [127.0.0.1]
>>> QUIT
221 2.0.0 NAME.host.MYSERVER.net closing connection
root@NAME[/etc/mail]$
You have new mail in /usr/mail/USER
 
Old 09-09-2009, 12:04 AM   #2
bathory
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Registered: Jun 2004
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Quote:
When i send mail to this particular domain, the box for some reason thinks that it's the mail handler and returns "user unknown" instantly.
What do the following commands return?
Code:
sendmail -bv user@dumbdomain.com 
dig mx dumbdomain.com
 
Old 09-09-2009, 01:22 AM   #3
hitcttd
LQ Newbie
 
Registered: Sep 2009
Posts: 2

Original Poster
Rep: Reputation: 0
Solved it!

Got it to go

Bathory: That was one of the places I looked initially, and it actually ended being the answer except not super obvious. Turns out that there was a reverse pointer that pointed the MX IP back to the main host record (which is the webserver). How or why that pointer was there? Who knows. In any case it basically created a loop. Explains why the server tried to authenticate. Also strange how it performed a lookup, found the MX IP, performed a reverse lookup and used the result! Isn't that strange or is that how it all works?

Thanks for the reply man!
 
  


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