Mail was designed as a gullable system, and this is generally abused
by spammers. Fighting spam is a balancing act between failures to
accept and reject. With the more refined identity model of the
IdentityHub, we have new tools to strike a better balance.
SPF is the technology that assures that mail only arrives from authentic
senders. One problem remains that slows down its introduction as a
hard filter, and that is email forwarding. This article nails the
integration of SPF with forwarding.