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mail queueing up with error smtp error 451

Posted on 2006-11-30
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Last Modified: 2012-05-05
Hi we have a SBS 2003 with Exchange 2003 and all of a sudden mail will not send, first i noticed the error (The connection was dropped due to an SMTP protocol event sink) when looking at the queues in exchange manager.
So i enables smtp logging and this error was logged in event viewer.

Event Type:      Warning
Event Source:      MSExchangeTransport
Event Category:      SMTP Protocol
Event ID:      7002
Date:            11/30/2006
Time:            8:37:53 PM
User:            N/A
Computer:      SERVER
Description:
This is an SMTP protocol warning log for virtual server ID 1, connection #77. The remote host "xxx.xxx.xxx.xxx", responded to the SMTP command "rcpt" with "451 Temporary local problem - please try later  ". The full command sent was "RCPT TO:<mail@mydomain.co.uk>  ".  This may cause the connection to fail.

For more information, click http://www.microsoft.com/contentredirect.asp.

So i tried to connect to my isp's smtp mail server via telnet and got this error

MAIL FROM:mark@customersdomain.co.uk
250 OK
RCPT TO:mark@mydomain.co.uk
500 unrecognized command
RCPT TO:mark@myotherdomain.co.uk
500 unrecognized command
RCPT TO:Mark@mydomain.co.uk
500-unrecognized command
500 Too many syntax or protocol errors


Connection to host lost.

any help would be appreciated

Mark
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Question by:genesisIT
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Expert Comment

by:Sembee
ID: 18050436
If you are sending email via your ISPs server, it would look like your ISPs mail server has a problem. You will need to speak to the ISP to find out what is going on.
You could try switching your email to deliver by DNS, you will probably find most email will be delivered, even if you are on a dynamic IP address. Some will fail and you will have to sit on those until the ISP has fixed their problem.

Simon.
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Author Comment

by:genesisIT
ID: 18051956
It's not the isp because i have many other customers using the same isp including myself and they are all fine it is just this one site that has a problem.
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Accepted Solution

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Sembee earned 500 total points
ID: 18052035
What has changed then?
Problems like this do not occur overnight unless something has been changed.
If the remote host is giving you back an SMTP error then it is an issue with that remote host. The local machine cannot generate that error unless something is interfering with the traffic.

Simon.
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