On Fri, May 02, 2014 at 06:52:05PM -0400, John R Levine wrote: > The problems are occuring at the end points, not at the IETF. For example, > aaron@xxxxxxx posts to a list, where one of the subscribers is > charlie@xxxxxxxxxxx. The list adds a subject tag and footer, as our lists > have done since forever, and remails it to Charlie. Comcast's DMARC > software observes that this message has an aol.com addresss in the From: > line, but didn't come from an AOL IP host (SPF) or has it a valid aol.com > DKIM signature, so Comcast bounces it. This isn't hypothetical; I've seen > exactly this in my logs. If you think about the inventives of the entities in question, it's really not that surprising. Yahoo and AOL will want to force people to use their web-based forums, so they have no incentive to make life easier for mailing lists. And Comcast has an opportunity to steal mail users from Yahoo and AOL by telling the world the solution is to use their comcast.net address, since they promise not to enable p=reject (even as they enforce it with a vengeance): http://postmaster.comcast.net/dmarcupdate.html - Ted