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STMP Error

Posted on 2010-11-23
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Last Modified: 2012-08-14
I have a user that sent an email and got the following response:

An error occurred while trying to deliver this message to the recipient's e-mail address. Microsoft Exchange will not try to redeliver this message for you. Please try resending this message, or provide the following diagnostic text to your system administrator.

#< #5.0.0 X-Postfix; host smtp801.microsoftonline.com[xxxxxxxxxx] said: 550 5.1.1 User unknown (in reply to RCPT TO command)> #SMTP#

Assuming the email address is valid, what is the problem, and what setting do I change from exchange 2007 management console?
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Question by:theogio
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Alan Hardisty earned 1000 total points
ID: 34197622
Check the users email address - it would appear you have either typed it in incorrectly, or the user has gone.

Another alternative is the servers at their end are clustered and you managed to find the one node in the cluster that doesn't have this particular user configured on it.

Alan
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Expert Comment

by:jfletchster
ID: 34197682
The Recipent Email Address doesnt Exist. "5.1.1 User unknown"
The server you have contacted as the desternation is not accepting the email as you are trying to send to an address that it cannot route or deliver too.

If 100% sure the address is correct then the Postfix server is probably using this message as a denial message due to some other reason such as the sender has been tagged as spam or has been blacklisted;
Check the domains at mxtoolbox.com
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Author Comment

by:theogio
ID: 34197718
How would I check and remove names from the blacklist?
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Expert Comment

by:jfletchster
ID: 34197744
www.mxtoolbox.com
This website had a blacklist checker, you can then contact the seperate companys listed that have you blacklisted and request removal if you are confidant that you are not sending spam email from your site, i.e. a virus or mail bot on you internal network or exchange server
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Author Comment

by:theogio
ID: 34197838
According to www.mxtoolbox.com blacklist checker we are fine with the exception of some timeouts on the last three

CYBERLOGIC       TIMEOUT      ERROR, Reponse code=2             0
EMAILBASURA       TIMEOUT                  0
SPAMRBL       TIMEOUT            0
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Expert Comment

by:jfletchster
ID: 34197916
To Check SpamRBL lists try this site;
http://www.anti-abuse.org/multi-rbl-check/

Blacklisting is only one option.
My next question would be;
Can you email anyone at the desternation company? or are you only having problems sending to this one user.
Can they (the destination company) send to you or your users without any problems, I would then try to reply to one of thier emails so the correct email address is used.
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LVL 76

Expert Comment

by:Alan Hardisty
ID: 34198011
Where on earth did Blacklists come into the equation when the error is Unknown User?

That is a complete Red Herring and should be ignored.
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Assisted Solution

by:mccrick
mccrick earned 1000 total points
ID: 34205897
what email client is being use?

What happens if the failing sender replies to a message from the failing recipient?

What happens if you temporarily set the SMPT to use another server such as smtp.google.com (with the correct credentials of course)?
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Author Comment

by:theogio
ID: 34229939
The user hasn't said anything new about the issue. I assume he had the wrong email address.
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