Just came across further arguments for this by a dreamhoster, and made
it a suggestion at panel.dreamhost.com, as follows. We'll see...
Custom header_checks (www.postfix.org/header_checks.5.html)
All I really want is the ability to REJECT incoming SMTP based on recipient.
Once a recipient-delimited ("email@example.com") address starts
getting spam, rejecting at SMTP level is much nicer than procmail to /dev/
null. (E.g. senders get notified it's no longer read.) This applies especially to
the spam-prone but necessary extension-free version ("firstname.lastname@example.org"
in this case).
This would solve the problem of those who wish postfix would support
another recipient_delimiter (see previous Suggestion: Allow "semi-catch-all"
emails like "email@example.com", 2005-05-16). Right now their only
option is to make domain.com a catch-all and then silently discard almost
everything in procmail.
"Semi-catch-all" aside, this would generally let us gracefully retire any
addresses that start getting spammed. See file /etc/postfix/header_checks
on a dreamhost machine -- it's just a bunch of lines like
/^From:.*@0451.com/ REJECT Message rejected due to site policy
so you could say something like
/^To:firstname.lastname@example.org/ REJECT Address retired, please use email@example.com
(Meanwhile, I'm still interested in advice on whether or not the procmail
workaround described in the parent post is a good way to go.)