550 No User Here

This is the error that comes back to those who try to send us e-mail

Sorry, we were unable to deliver your message to the following address.

Remote host said: 550 No Such User Here [RCPT_TO]

Windows Server 2003 SBS / Exchange 2003
We are using Barracuda / SpamHaus RBL

This applies to at least 3 of our users and these users have been receiving mail previously with no problems. These users do exist in the Active Directory as well as Exchange.

Looking through Event Viewer I see a few error with MsExchangeTransport / SMTP Protocol EventID 7010 such as

This is an SMTP protocol log for virtual server ID 1, connection #174. The client at "" sent a "helo" command, and the SMTP server responded with "501 5.5.4 Invalid Address  ". The full command sent was "helo .mshome.net".  This will probably cause the connection to fail.

However most of those according to blacklists searches are coming from spammers or virus spreaders

I also have a lot of DNS events 6702 (DNS server has updated its own host (A) records.  In order to ensure that its DS-integrated peer DNS servers are able to replicate with this server, an attempt was made to update them with the new records through dynamic update.  An error was encountered during this update, the record data is the error code.
If this DNS server does not have any DS-integrated peers, then this error
should be ignored. )

There is only one 1 AD in this domain and its not replicating to any others. So im ignoring this.

Restarting the server temporarily fixes this, thats not an aceptable solution however. happens almost every day.

Who is Participating?
Shreedhar EtteCommented:

I suspect the user must have typed the wrong mails id.

Can post the full NDR?

Anti-MhzAuthor Commented:
Delivery to the following recipient failed permanently:


Technical details of permanent failure:
Google tried to deliver your message, but it was rejected by the recipient domain. We recommend contacting the other email provider for further information about the cause of this error. The error that the other server returned was: 550 550 No Such User Here (state 14).

----- Original message -----
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Anti-MhzAuthor Commented:
I just sent a message to myself from gmail account, it went through. I replied to it. It appeared iin my gmail account, i replied to it again, it came back to gmail account with 550.

Could there be some kind of limiting filter on Exchange 2003 on how many e-mails from  a specific address (or domain) can be received per lets say minute.
Anti-MhzAuthor Commented:
I should add that locally (emails sent within the domain) there appears to beno problem.
Mohammad Ishtyaq KhatriCommented:
If you are using outlook at client end, In the settings manually enter the user name and password for outgoing ID should be same as incoming. Check mark to use smtp authentication and spa. may be this will help you to resovle this issue.
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