I took a different approach. I left the bounce detection on but switched all
@yahoo.com accounts to digest mode.
Since the mail now comes from the list instead of the @yahoo.com sender there
are no rejections. Not a perfect
solution but it prevents harm to non-(_at_)yahoo(_dot_)com list participants.
I don't see how that helps. The problems occur when a list message
with "From: blah(_at_)yahoo(_dot_)com" is delivered to a Gmail or Hotmail or
Comcast address which follows the DMARC advice and bounces the
message.
R's,
John