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SMTP conversation stops with ICMP error

I posted the following on an exchange forum:

>I am running an exchange 2003 server. Some users have not been receiving mail with the error message "status=deferred (conversation with x.x.x.x) >timed out while sending RCPT TO". Using a packet sniffer I was able to trace the SMTP conversation.

>The conversation carries on ok up until the point my server sends the command "Start mail input; end with <CRLF>.<CRLF>". The external server >responds with an ICMP error message "Type 3: Destination unreachable. Code 3: (Port unreachable)".

>This problem is not specific to a particular sending domain.

The reply to the post was that this was not an exchange problem but a routing error. We have an 1800 series cisco router between the internet and our mail server. Just to be clear - the ICMP error message is sent by a router/server ouside our network.

My question is has anyone experienced this kind of error and how did they resolve it?

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Hall of Fame Cisco Employee

SMTP conversation stops with ICMP error

Hello,

This sounds more like some kind of firewall sitting behind the SMTP client and the Exchange server. The ICMP message is sourced by a particular IP address - therefore, I recommend inspecting the configuration of the device with the IP address that sent the ICMP message.

Best regards,

Peter

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