AccuSpam wrote:
8. But the bigger problem for "-all" in SPF, is how will an ISP ever know that
all of it's users are sending all their email over the approved IPs? It is simply
impossible for an ISP to ever know that. An ISPs user can access the internet with a
different ISP, and then set their From: address to the first ISPs domain. I do that all
the time when I travel.
If I were running an ISP, I'd tell people, "don't do that." In fact,
this is exactly the position I take at work. How can we claim any kind
of accountability for mail if we don't control the servers it originates
from? IMHO this only prohibits something that was a bad practice to
begin with.