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check the receive connectors on your exchange server<br />
make sure that at least one has the ip address where you are connecting from listed in the remote ip ranges and the anonymous users is selected in the permissions group
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can you telnet from exchange server itself ?<br />
<br />
telnet localhost 25 ?<br />

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We rebooted the server and this fixed the problem 
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Hi when I try to telnet to my exchange server internally I ge the following error:<br />
<br />
421 4.3.2 &nbsp;Service not available , closing transmission channel.<br />
<br />
What does this mean?
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Hi when I try to telnet to my exchange server internally I ge the following error:

421 4.3.2  Service not available , closing transmission channel.

What does this mean?

Exchange  2007 error telneting to my exchange server internally

Exchange is the server side of a collaborative application product that is part of the Microsoft Server infrastructure. Exchange's major features include email, calendaring, contacts and tasks, support for mobile and web-based access to information, and support for data storage.