[Mailman-Users] Gmail and DMARC

[Stephen J. Turnbull]

Jim Popovitch writes:

 > TBH, I'm not sure what else there is to look for. :-)  GMail, every so
 > often, is telling my Mailman that it needs to Auth in order to reflect
 > From:gmail to other gmail customers.  It's like DMARC without
 > following the DMARC standard (GMail has a p=none policy).

Is it possible that those users are using their GMail address from a
non-Google host?  That would explain the intermittent nature of the
challenge -- it doesn't have the GMail DKIM signature that identifies
GMail-from-GMail messages.  And it would also explain why it "looks
like" DMARC, since DKIM is one of the underlying protocols used to
implement DMARC.