Cannot connect to port 25 on a Mail server
Problem:
Cannot connect to port 25 on an MS Exchange server to use its SMTP service. A telnet test gave the following error:
telnet xx.xx.xx.xx 25
Connecting To xx.xx.xx.xx…Could not open connection to the host, on port 25: Connect failed
Background & Analysis:
One of my batch scripts used blat to send emails. However, I could not use the SMTP service on the Exchange Server. After liaising with the Exchange and Network administrators, we determined the following:
- There was no firewall between my machine and the Exchange server and a tracert completed quickly in just 2 hops.
- There was no firewall on the Exchange server.
- The firewall on my machine was turned off.
- The SMTP service was listening at port 25 on the Exchange server and was functioning properly.
Solution:
The McAfee Anti-Virus log on my machine had the following entry:
16/12/2010 12:41:02 PM Blocked by port blocking rule C:\WINDOWS\system32\telnet.exe Anti-virus Standard Protection:Prevent mass mailing worms from sending mail xx.xx.xx.xx:25
So, it was the McAfee anti-virus software that blocked outbound connections to port 25. To resolve this problem, you can add an exception to the anti-virus policy that permits your mail program (in my case, it was blat) to initiate connections to port 25 (recommended) or you may disable the anti-virus (not recommended).
Root Cause:
The Anti-virus software on the source machine had a policy enabled which prevented outbound connections to port 25.
NOTE:
(1) The solution above describes a successful problem-solving experience and may not be applicable to other problems with similar symptoms.
(2) Your rating of this post will be much appreciated. Also, feel free to leave comments.
Tagged with: cannot connect to port 25 on MS Exchange • Connect failed • Could not open connection to the host • on port 25: Connect failed • Prevent mass mailing worms from sending mail
Filed under: Application Software • Windows
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