Exchange Disconnecting on EHLO with remote telnet

Posted by Timothy Baldridge on Server Fault See other posts from Server Fault or by Timothy Baldridge
Published on 2010-02-17T23:00:25Z Indexed on 2010/04/23 14:04 UTC
Read the original article Hit count: 453

Filed under:

exchange

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exchange-2007

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microsoft-smtp

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c#

When I go to the local terminal on my Exchange box (SBS 2008) I can do this:

telnet 127.0.0.1 25
220 Exchange banner here
EHLO example.com
250 Server name

However when I go from another box, or from the actual IP of the server I get this:

telnet 192.168.21.20 25
220 Exchange banner here
EHLO example.com
421 4.4.1 Connection timed out

Connection to host lost.

The odd thing is, this server is currently in production and working fine (receiving mail for our entire domain). But my C# programs can't send mail to it (they get this same error).

Any ideas?

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