AccuSpam wrote:
However, consider that supporting "-all" for SPF (in order to give SPF similar
anti-forgery power) for all domains is also going to require upgrades to all MUAs in
order to integrate with many different flavors of SMTP authentication at many different
servers.
Most server software supports SMTP AUTH, though it isn't always switched
on. Most clients also support SMTP AUTH. There's no need to support
multiple systems. The only other common system I'm aware of is
POP-before-SMTP, but that's pretty crude and I'm not sure it really
counts as authentication. It doesn't require any special MUA support,
though. ;)