> -----Original Message-----
> From: Pfefferkorn, Pete (PFEFFEPE) [mailto:[EMAIL PROTECTED]]
> Sent: Friday, July 12, 2002 1:38 PM
> To: Exchange Discussions
> Subject: Reverse DNS and Exchange
>
> Exchange 5.5
>
> I'm a little confused on Reverse DNS. I kind of understand the concept
> that
> with Reverse DNS enabled the Mail from: entry must resolve to a valid
> domain
> or it will get rejected. Some I have some basic questions:
>
> I take it Exchange 5.5 does not support Reverse DNS?
Does not support it in that it doesn't reject mail from a server that
doesn't have a valid PTR? No. You'd reject a heck of a lot of potentially
legitimate mail that way.
> How about Exchange 2000?
IBID
> How effective is Reverse DNS to help the control of Spam?
About as effective as a screwdriver in building a house.
> What problems/issues will we encounter if we do implement reverse DNS in
> some for on front end servers whatever it may be?
You'll reject mail from thousands of misconfigured mail hosts, with a strong
bias towards smaller shops.
> What about users who have POP and have their return address set to be
> something other than their ISP but they use the ISP as the relay?
You could potentially reject those as well depending on the filtering method
employed.
> When they state the Mail From: they mean the From: in the display area and
> not all the routes?
I believe they generally mean the RFC821 Mail from.
> If you have a front end relay like PMDF/VMS which relays first.last@domain
> to a messaging system, reverse DNS will not prevent spam to the receiving
> systems since it will also validate from the relay?
Unless that server does the filtering or you use a product which will filter
based on IP addresses in the headers.
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