MDAEMON Server 7.2 - can't send email to certain email addresses

We are running MDAEMON SEVRER 7.2 on a Windows 2003 server.  For some reason we can receive messages from a certain email domain but when we send or reply to them we get the following error:

--- Session Transcript ---
 Thu 2008-01-31 12:29:50: Parsing Message <xxxxxxxxxxxxxxxxxx\pd50000728151.msg>
 Thu 2008-01-31 12:29:50: From:
 Thu 2008-01-31 12:29:50: To:
 Thu 2008-01-31 12:29:50: Subject:
 Thu 2008-01-31 12:29:50: Message-ID: <>
 Thu 2008-01-31 12:29:50: MX-record resolution of [] in progress (DNS Server:
 Thu 2008-01-31 12:29:50: P=010 TTL=(70) MX=[] {}
 Thu 2008-01-31 12:29:50: Attempting MX: P=010 TTL=(70) MX=[] {}
 Thu 2008-01-31 12:29:50: Attempting SMTP connection to [ : 25]
 Thu 2008-01-31 12:29:50: Waiting for socket connection...
 Thu 2008-01-31 12:30:12: Winsock Error 10060 The connection timed out.
 Thu 2008-01-31 12:30:12: This message is 50 minutes old; it has 0 minutes left in this queue
 Thu 2008-01-31 12:30:12: Primary queue lifetime exceeded; message placed in retry queue
--- End Transcript ---
: Message contains [1] file attachments

In coordination with the admin at that domain we have confirmed that the IP address is valid and that they have allowed us to enter through their spam and spyware blocker.  I am at a loss here.....
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Strange, but at least the problem is limited to one domain, which should make it easier to pinpoint.

Try this:
1. Can you ping the destination server's IP?

2. Make a telnet connection on port 25 from your server to the destination server:
telnet 25

You should see the beginning of an SMTP transaction - I get this:
220 ESMTP MailMarshal (v6.2.2.3503) Ready

If the connection times out, it means that you cannot talk to that IP address or they are blocking connections from your IP. At this stage, it is unlikely it is the spam filter kicking in, as the receiving mailserver has not received anything from you (no sender, no mail body), so it cannot analyse anything.

At this point, all the receiving mailserver knows about you is your IP address. Many mailservers implement IP address blacklisting, sometimes banning sites that connect too often. Do you send many emails to this domain?

Also, some mailservers block connections from IP addresses on which reverse DNS lookup cannot be performed. Is yours set up correctly? To check, go to and use the Reverse Lookup tool to check your mailserver's IP address. It should resolve back to your mailserver's domain name.

See how you go and let me know please.
I offered extensive troubleshooting steps - no feedback from the poster.
robdijoAuthor Commented:
Your solution didn't resolve my situation.
It was not a solution, it was the beginning of a troubleshooting process and there was no feedback given afterwards.
However in the interest of keeping EE clean, this thread should be removed, as it does not lead to a solution.

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