Watermarking and spoofed sender address

[Robert Lopez]

I understand watermarking is to defend against "joe job blowback". I think
I understand that blowback problem is when email is sent, using for example
my address, to many other domains and all the flack (blow back) comes back
to me.

I am wondering if this watermarking is of any use in a type of SPAM we now
frequently see. It is where email is sent to a list of addresses, all at
our domain, and the from address is also the first address in the address
list. Everyone else thinks the first person sent it. Our gateways send such
email to Exchange and any communication back to the sender is entirely
within Exchange and never comes back through the gateways again.

In this kind of SPAM I have always considered it of no use. Am I wrong in
my thinking?

-- 
Robert Lopez
Unix Systems Administrator
Central New Mexico Community College (CNM)
525 Buena Vista SE
Albuquerque, New Mexico 87106
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