North American Network Operators Group
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Re: SMTP no-such-user issues

  • From: Steve Bertrand
  • Date: Tue Jun 17 07:12:48 2008
Steve Bertrand wrote:
Hi everyone,

We are experiencing an issue in regards to SMTP MTA relay responses regarding 'no such user', and it *apparently* appears to be only occurring when a particular site attempts to deliver email to us. Any advice on how to further troubleshoot my issue would be greatly appreciated.

Because I have been inundated with off-list replies, I'll post my findings here.

First, a screen cap of me composing a message, in which two of the addresses are easily identified as valid, and two are clearly not:

http://ibctech.ca/nanog_smtp/hotmail_compose.jpg

...when I sent it, I received thus:

http://ibctech.ca/nanog_smtp/hotmail_response.txt

So, we'll try it from a different server:

http://ibctech.ca/nanog_smtp/local_compose.jpg

...hmmm, I received the message at [email protected] (even though the To: field was cropped out of the jpg) this time, and my server generated the following....AFAICT, correct 551 error(s):

http://ibctech.ca/nanog_smtp/local_err.txt

I'm willing to provide any more documentation required in order to get this issue sorted.

Thank you everyone, I truly appreciate it.

Steve