Exchange 2003, Can receive email, but cannot send email from outside the office

I am running Exchange 2003 sp 2 on Windows 2000 sp4 OS. When I am outside the office I can receive email, but I cannot send. I get the following generic error: Task 'mail.aipla.org - Sending' reported error (0x800CCC0F) : 'The connection to the server was interrupted.  If this problem continues, contact your server administrator or Internet service provider (ISP).'  This has been going on for about 2 months now. I tried to telnet from my home to my Exchange server and had no luck. Also, when I tried to telnet from the exchange server, I had no luck.

Everything works fine when I am in the office. I have asked others to check from their homes using a different ISP and they are having the same problems.

Any thoughts/suggestions would be greatly appreciated! Thanks.
aiplaIT ManagerAsked:
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elbereth21Commented:
Hi aipla,
since you cannot telnet to the Exchange server, there seems to exist a possible problem with firewall configuration or an IP filter on the addresses of the computers allowed to relay mail through Exchange.
Anyway, have you already seen this article?
http://support.microsoft.com/kb/813514

Elbereth.
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elbereth21Commented:
The problem reported might also depend on a patch for Internet Explorer issued in April:
http://www.experts-exchange.com/Applications/MS_Office/Outlook/Q_21821263.html
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SembeeCommented:
Are you using Outlook as an Exchange client or as a POP3/SMTP client?
If it is the latter, then the question you have to ask is why? As you are on Exchange 2003 the preferred remote access method is RPC over HTTPS. This gives you full access to the features of Exchange and also means you are not attempting to relay email through your Exchange server over the internet.

The error message certainly indicates that something is either blocking or disrupting the connection. SMTP over the internet to your Exchange server for relaying email is not something that can be relied upon. Many ISPs block SMTP traffic from their networks, and you have to use their SMTP server to send email. You can get round this by using a VPN.

Simon.
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aiplaIT ManagerAuthor Commented:
The SMTP part of the POP3 client does NOT work when I use VPN, but the Exchange client does. I am not running any third part firewall on this system and the SMTP connection broke months after the IE patch in April 2006 (referencing the suggestions by Elbereth). I am not familar with telnet, but do think it's unusual that I can't telnet to my exchange server and from my exchange server. Is there a way you can check to see whether or not my settings are correct?
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SembeeCommented:
There should be no reason why SMTP works off the VPN but not on the VPN, unless your dns isn't set correctly and the host in the SMTP server doesn't resolve to the Exchange when on the VPN. That is quite common and is fixed by setting up a split DNS system.

Being unable to telnet to the server on port 25 is also quite common as some antivirus products have started blocking port 25 as part of their protection. McAfee and Symantec products do that, and some others as well. You may want to look at the AV configuration to see if it is blocking port 25 (Internet Email) and if so, it should be disabled on the Exchange server.

Simon.
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