Using results of dkim for gmail

From: Steve Fatula <compconsultant_at_yahoo.com>
Date: Wed, 10 Aug 2011 13:50:04 -0700 (PDT)

So, I want to block (yes, not including, blocking) email clients based on some logic, can anyone tell me why this would be flawed....

My understanding is that gmail ALWAYS signs messages via dkim, as does ebay and paypal. In 2008, gmail started blocking ebay and paypal messages that did not pass dkim checking. I'd like to do something similar. So, is there any flaw if I decide to:

If an email comes from gmail or ebay or paypal, and, it has no dkim signature, reject the message

Note, I didn't even say it had to pass. It would seem that there should be no chance of it not being signed, right? So, any message meeting my criteria is 100% forged.
 
Steve
Received on Wed Aug 10 2011 - 20:50:18 PST