check_relay cannot return temporary errors.
The temporary error is logged in the sendmail log, but on the SMTP
protocol level, sendmail returns '550 Access Denied'.
Reviewed by: jmb
Submitted by: Tor Egge <Tor.Egge@idi.ntnu.no>
break each ruleset into identified sections. (called groups).
note which groups can be reordered.
each group accepts and returns the same strings,
as much as possible.
reactivate Paul Vixie's RBL (in check_mail)
add rules to limit mail relaying to a list of hosts and domains
in the R class (check_rcpt, not active on hub.freebsd.org)
Submitted by: jmb
