On Wed, 1 Mar 2017, Carsten Bormann wrote: > On 1 Mar 2017, at 20:18, Michael StJohns <mstjohns@xxxxxxxxxxx> wrote: > > > > eventually customize the confirm message based on provider > > Better: Send the subscription confirmation message with attributes that cause a DMARC-honoring provider to discard it :-) > (No programming required :-) No, that is worse as it insures support costs and more noise on this list.