Set aside the theoretical and philosophical discussion
against text RRs
for a minute and just look at the practical issues.
While I've preached small responses and simple yes/no records, I'd like to
know if a small TXT record vs a larger TXT record makes a difference.
whatever pops
out of this effort are already doing a bunch of lookups; I
look for any
MX/A for the HELO domain, the MAIL FROM domain, and the From: domain
already (via Postfix/SpamAssassin filters), and also lookup a bunch of
blacklist entries including SpamCop, cbl.abuseat and spamhaus
in Postfix and a bunch more inside SpamAssassin.
I'd hope that all those BLs would die off, having served their purpose, once
MARID becomes widespread. Domain based BLs would become more popular.
You've seen the numbers for DMP. It doesn't take much to extrapolate them
for SPF - just add the extra size of the SPF record vs the DMP record not
including the MX lookups that SPF imposes - or better yet, in the
non-wildcard DMP scenario replace the domain-only check with a MX check which
would probably take from the same bandwidth to twice the bandwidth. What
does an average of 4% increase in bandwidth, not including caching, compared
to SMTP alone do to your guesstimates? 6%? And then after eliminating the
BL lookups?
Whatever number comes out of that will probably be wildly inaccurate, but it
would give us a medium to worst case guesstimate of bandwidth usage short of
actually measuring it.
I only want to know what it does to your numbers. I'm not shooting down the
argument - I'll let the numbers do that or not do that.
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Sometimes it's hard to tell where the game ends and where reality bites,
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