Re: SPF and bouncing

> Back in 2001, I was acting as an unofficial advisor to my own ISP on spam
> issues.  The admin there asked me about the safety of deploying sender
> verify on Exim, in order to reduce a flood of deadletters that was
> annoying him.  (Note: this was oridinary sender verify, where just the
> existence of an MX is checked -- not the abusive callout feature.)

As late as 2007, I was helping experienced antispam providers get
scheduled address list dumps from Exchange and other mailbox servers
up to the edge (via FTP). I wouldn't call it state-of-the-art for that
time, exactly. But there were def'ly a wide swath of people who were
great at catching spam, but who couldn't prioritize/mandate the
address list sync because it required help from the clients, many of
whom were small businesses with no knowledge of how to set up a
scheduled upload, etc., and others large businesses who took their
sweet time setting up a Guest account to query LDAP and so on.

These things are all easier now, though it's still true that some
"intrusion" by the provider is necessary... and rightly so because the
address list should never be public queryable.

-- Sandy