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

Posted on 2004-10-19
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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?

Thanks
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Question by:ROUTEPRO
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scampgb earned 125 total points
ID: 12348139
Hi ROUTEPRO,

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?
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by:scampgb
ID: 12348170
ROUTEPRO:
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
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by:adamdrayer
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.
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Author Comment

by:ROUTEPRO
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.
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by:scampgb
ID: 12369980
Glad I could help :-)
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