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Can't telnet smtp through the firewall but can internally.

Posted on 2009-05-06
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Last Modified: 2012-05-06
Exchange 2003 behind ISA 2004.  Everything was working but now I can't receive email.

telnet smtp into the server on the inside network is ok

telnet smtp through the firewall suddenly doesn't work.


Any help would be appreciated.

Thanks.
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Question by:gateguard
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2 Comments
 
LVL 35

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Bembi earned 1000 total points
ID: 24319329
You mean, you can not telnet from the external interface to your Exchange? (As you said, you cannot receive).  I assume you can send, right?

If you telnet yoir Exchange through ISA, you telnet the listener port for exchange on ISA, which forwards the request to the internal server. This is done by a server publishing rule.

First at all, I would reboot the ISA (assume you have done this).
Check, if your ISA is listening on port 25
 
netstat -a -n -p TCP
You should get a line like:
TCP ExternalIP:25 0.0.0.0. Listening

You should not get
TCP 0.0.0.0:25 0.0.0.0. Listening

also try  netstat -a -b -n -p TCP
to see, which process is listening to port 25,

Have you installed / changed something, especially virus scanner with mail scan? As ISA has to listen on this port, no other service should use this port.
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LVL 51

Assisted Solution

by:Keith Alabaster
Keith Alabaster earned 1000 total points
ID: 24319419
I would also check your external router - has someone made a change? Is it still forwarding port 25 to the ISA external IP address?

open the ISA gui - select monitoring - logging - start query.
Try the external telnet on port 25 again - what do you see in the log?
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