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Beginner

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

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