[John Keown]
That is why and where smtp authentication comes into play. With smtp
authentication the hijacker cannot authenticate and therefore cannot send
from example.com return address.
This is an additional administrative burden and source of configuration
errors.
ISPs (in addition to SPF) has to maintain SMTP AUTH and distribute/update
passwords (or use client SPF records during relay)
For all clients! Even for those who have our MTA on DSL and use ISP router
as relay.
This will make SPF non-reliable if ISP client configured SPF, but ISP has
not adopted SMTP AUTH yet.
This will increase initial adoption time.
--
Andriy G. Tereshchenko
TAG Software
Odessa, Ukraine
http://www.24.odessa.ua