In <opsrcdkizm7v2np4(_at_)lmail(_dot_)pscs(_dot_)co(_dot_)uk> "Paul Smith"
<paul(_at_)pscs(_dot_)co(_dot_)uk> writes:
Maybe SPF (or something like it) should allow signed messages to
'override' SPF - so mobile users from domains can fall back to message
signing, without requiring that overhead for the majority of users who
either aren't mobile, or who relay through their home mail server (as
we do when we're mobile), so for whom the basic SPF will work
effectively.
The SES project is one such system that allows cryptographic
signatures to be used during SPF checks to make sure roaming users
aren't hurt. This is outline in section 9.3.1.2 of the spf-classic
draft.
-wayne