Greg Connor wrote:
2. There *might* be some cases where mfrom checking would work and PRA
checking would fail. Therefore it's better to avoid any cross-pollenation
of the strains.
2a. I know of some actual cases and they are not trivial.
In mail from Yahoo Groups (yahoogroups.com) the PRA is the original sender.
Most probably Yahoo will not add a Resent-Sender: or Resent-From: header.
This means that all mail in a Yahoo Group from a domain that publishes an
SPF record will be rejected by any MTA that does PRA checking.
So if MTA's are going to use the currently published SPF records for PRA,
then mail through Yahoo Groups (and probably other mailing lists) will be
rejected and therefore the domain owners will remove there SPF records.
Roger