Exchange 2003

Posted on 2009-04-27
Medium Priority
Last Modified: 2012-08-14
How do I turn off allowing a user from doing a telnet to port 25 to test the sending of email in exchange 2003. I was looking at some articles and it seems that in order to fix this i would have to go into ESM >>> Protocols >> SMTP >>> right click on Default SMTP Virtual Server properties and click >>> access tab >>> authentication >> uncheck Anonymous access. Will turning on TLS solve this issue. Can you please direct me to a guide that will show me how to do this?  Does anybody have any other suggestions on how I can do this?  

Question by:vferreira71
LVL 65

Accepted Solution

Mestha earned 2000 total points
ID: 24244954
In short - you can't.
There is no difference to a user doing a telnet test to the server receiving email.
If you turn off anonymous then you will not receive email from outside.
If you enable TLS then you will also stop your server from receiving most email.

You could add your local subnet to the connection restrictions on the SMTP virtual server, but that needs to be done with care to ensure that you don't block legitimate email. However a user determined enough to test thing will not find that much of a barrier.

LVL 30

Expert Comment

by:Britt Thompson
ID: 24244983
Turning on TLS will not prevent people from using telnet to access port 25. If you uncheck Anonymous access I'm pretty sure you'll stop receiving mail altogether.

I believe one of the best ways to block traffic on port 25 as much as possible is by using a SPAM filtering service like AppRiver's Secure Tide or postini. In this case you'll know exactly what IP's your mail will be coming from and you can block traffic to everything but the IP's of the filtering servers delivering mail to your server.

Here's AppRiver's instructions for that: http://support01.appriver.com/KB/a39/limiting-inbound-smtp-traffic-except-from-apprivers-servers.aspx

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