Twilley, Jack writes:

I have been sponsored by an organization to port the existing DMARC code from Mailman 2.1 to Mailman 3. While my primary responsibility is to satisfy the organization's requirements, it is very important to me that the resulting product be a viable candidate for upstream.

I would appreciate any constructive guidance on how to best achieve my goals.

I think the main issue will be any changes from Mailman 2's "Handler" API to Mailman 3's "Handler" (message-altering) and "Rule" (non-mutating) APIs, and how to communicate between them if both rules and handlers are used.

Of course you're also welcome to do algorithmic and style cleanups (the original from_is_list implementation was submitted by a third party and we were in a hurry to do something so the style is suspect -- I admit haven't looked at it, but somebody[tm] should :-).