On 11/30/2015 2:51 PM, Ted Lemon wrote:
> Why would I be relaying mail on?   Only for a mailing list.   For the mailing 
> list, what I want SPF to validate is that the mail came from the mailing 
> list. 


That's a common misconception.  It leaves out a variety of other, valid
scenarios.

The most obvious is mailbox aliasing, such as for vanity addresses such
as university alumni associations provide.

Email is store and forward, and this can and does mean transit across
/multiple/ independent administrative domains.  The fact that the vast
majority of mail goes directly (one hop) from origin AD to the
recipient's AD does not mean it is reasonable for anyone to make
systemic design decisions that constrain that fundamental flexibility.

IMO an essential design benefit in many/most aspects of Internet
technologies is avoiding making any more global assumptions (or
requirements) than essential.  "Deferring to the end systems" is a very
broad-based design requirement and it includes minimizing assumptions
about the transit infrastructure.

d/
-- 
Dave Crocker
Brandenburg InternetWorking
bbiw.net

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