Here's a quick, off-the-cuff comparison of these two approaches:
LMAP Purpose: prevent domain name forgery of HELO/FROM
Domain Keys Purpose: prevent domain name forgery within message headers
LMAP Costs: single DNS lookup and maybe a comparison
Domain Keys Cost: DNS Lookup, cryptographic function, possibly once per
transitted MTA
LMAP advantages: simple to implement - replace rDNS/A lookups by current MTAs
LMAP disadvantages: continuing question of forwarding in various scenarios
DK advantages: prevents forgery in forwarded situations, such as if a
mailing list owner inserts a forged message on the list.
DK disadvantages: high burden of software implementation, requires receipt
of DATA before an authoritative check can be done
I think that if the design of these two approaches is coordinated, they can
be quite complimentary. Unfortunately, I haven't seen any Yahoo
representatives on this list yet, so I'm a little bit worried.
Philip Miller
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