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I have a dedicated server with SMTP unblocked on port 25 and POP3 unblocked on port 110.

 

In my webmail application (Horde) everything is fine.  Email works as expected.  In my home computer in Outlook however, I can only receive messages.  When I send, I get an error.  I can't even open command prompt and telnet example.com 25 though I can telnet example.com 110 just fine.  Both of these ports are unblocked in the webmin firewall.  My only guess is that the SMTP server doesn't know how to communicate with remote hosts???

 

I opened an SSH connection to my server and typed in HELO example.com and ELHO example.com and I get nothing.  In fact it says: HELO: command not found.

 

Microsoft released this article which seems to address the error number I get with Outlook...however it doesn't in my case.  (http://support.microsoft.com/kb/191687)

 

Does anyone know what this means and how to fix it?

 

Thank you!

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  • 3 weeks later...

Judging by what you're saying, it sounds like your ISP is blocking outgoing communications to third party mail servers on port 25.

 

Just to make sure, you can flush the iptables firewall on the Linux server by:

iptables -F

 

You can also configure your MTA to listen on another port besides 25.  What mail server software are you running?

I am using the latest version of sendmail on a Fedora Core 5 box.  Port 25 is open when I run netstat from the command line via SSH.  I've tried using port 587 for outgoing via Plesk Control Panel's assistance.  I also allowed connections incoming to destination port 587 in the Webmin firewall for this.  I configured Outlook to work with outgoing 587 and it still wouldn't work :/  Should I flush the ip tables?  Is this similar to flushing dns on a local machine or will this wipe my server firewall configuration?

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