[whpalmer4]

The message looks fine. The behavior you describe (properly formatted message, call to process_message, but no action appears) suggests that you do not have the account from which the message was sent listed in the set of authorized accounts in the OmniFocus preferences for Mail. You get a call to the Mail rule every time a message comes in addressed to OmniFocus (either via the +omnifocus address or the subject line starting with the configured text), and that causes the call to process_message to happen. OmniFocus checks at that point to make sure the sender is on the list of authorized accounts, but no diagnostic message is logged if it is not, it simply discards the request.