Telnet to port 25 does not work from any location  exchange 2003 / exchange 5.5

Posted on 2004-10-19
Medium Priority
Last Modified: 2010-03-18
Hi There,

I have 2 networks in my office. One has an exchange 5.5 and another has exchange 2003.

From my house I can not telnet to port 25 on any of the two servers.

If I telenet from a diferent location then my house it works fine.

Can it be my ISP blocking it? I have earthlink at home.

If so, is there a way to bypass that?  And why would they do that?

Question by:ROUTEPRO
  • 3
LVL 15

Accepted Solution

scampgb earned 375 total points
ID: 12348139

I suggest that you try a telnet test to somewhere other than your office machine.  Try these for example:
hotmail.com     MX preference = 5, mail exchanger = mx2.hotmail.com
hotmail.com     MX preference = 5, mail exchanger = mx3.hotmail.com
hotmail.com     MX preference = 5, mail exchanger = mx4.hotmail.com
hotmail.com     MX preference = 5, mail exchanger = mx1.hotmail.com

Many ISPs block port 25.  They'll generally say it's to stop spammers, although most of them will unblock it for you if you pay extra.

Does that help?
LVL 15

Expert Comment

ID: 12348170
I found a Mac-based article on Earthlink's website which suggests that they do block outbound connections on port 25.
Take a look at : http://support.earthlink.net/mu/1/psc/img/walkthroughs/macintosh/os_x/email/mail/7177.psc.html
LVL 15

Expert Comment

ID: 12348357
25 is a very highly blocked port for ISPs.  They say its for spam purposes, but its more for you running a spamming server or relay than it is for incoming spam.

Author Comment

ID: 12365159
It is in fact Earthlink blocking the port.

I connected using a dial-up of a different provider and I was able to use telnet with no problem.

Thanks for the comments.
LVL 15

Expert Comment

ID: 12369980
Glad I could help :-)

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