Watermarking and spoofed sender address

[Peter Bonivart]

On Fri, Mar 22, 2013 at 5:50 PM, Robert Lopez <rlopezcnm at gmail.com> wrote:
>> IF you are whitelisting emails by address and NOT adding in a directional
>> element
>
> I have been looking at the MailScanner book.
> I see the Rule Sets Example section and the "Contains a 'direction'".
> It has not yet hit me how and where to write such a rule.
> Would this take a custom function or do you believe it may be done with (a)
> rule(s)?

If you use a rule like "From: marketing at cnm.edu yes" for whitelisting
you risk letting spammers in if they use that address when they mail
you (from internet). You need to add "direction" like "From:
marketing at cnm.edu and From: 1.2.3.4 yes", 1.2.3.4 in this example is
the IP address of your mailbox server, e.g. Exchange. If it has that
address and comes from your own server it's safe to whitelist. Ok?