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Exchange serve configuration - require FQDN in SMTP address

Posted on 2006-10-26
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Last Modified: 2010-03-06
Good morning:

We are currently running an Exchange 2003 server and I wanted to force messages created by some of our automated tools to use the FQDN or fail.  For example, you can telnet on port 25 and send a message as follows:

telnet ... 25
ehlo
250 OK
mail from:rscholl
250 2.1.0 rscholl@metratech.com....Sender OK
rcpt to:rscholl
250 2.1.5 rscholl@metratech.com
data
354 Please start mail input.
subject:<test>
all bad, sender was not FQ
.
250 Mail queued for delivery.
quit
221 Closing connection. Good bye.

The question is:  Does enabling the reverse DNS resolve the issue?  Is there a more elegant method?  What else is affected in the process?

Thanks in advance,

ray
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Question by:MetraTechIT
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Sembee earned 250 total points
ID: 17829355
The reverse DNS option in Exchange is close to useless. It doesn't enforce anything, except write a line in the header that reverse DNS failed. I don't think I have it enabled on any of my sites.

You would have to use a third party tool that can do reverse DNS lookups and drop the connection if it doesn't match or isn't valid.

This will of course have an impact on all of your email - as you will need to implement it on all SMTP Connections to be of any use. That could mean you are dropping valid email messages. If you do deploy a solution, make sure that you create text in the NDR message that is sent back that explains why the connection was dropped.

Simon.
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Author Comment

by:MetraTechIT
ID: 17833458
OK, so can anyone suggest the best solution for forcing FQDN in the SMTP from address?
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LVL 104

Expert Comment

by:Sembee
ID: 17834654
Its a standard anti-spam technique, so any tool of that type should be able to do it. I believe that GFI Mail Essentials can do that test, as can ORF from Vamsoft.

Simon.
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