Added penalty for FQDN not resolving to client IP.
Added special handling for bounce messages that bypass many checks, but are only accepted from a list of IP addresses in the config file.  (i.e. Only servers authorized to send for you should send you bounces.  Spammers ruined it for us.)  Also relaxed the enforcement of the FQDN of the client resolving to the IP address of the client, per recently discovered (to me) language in the SMTP RFC.
Squash this with the previous one.
Workaround for PublicDomainRegistry not answering for domains they are the registrar for.
Catch exceptions from a race between two threads inserting the same IP into the DB.