SAC,
Greylisting has been added to postfix to try and reduce the amount of spam that we are seeing.
Postgrey was installed and configured on www.osgeo.org the details on how this was done are here,
http://trac.osgeo.org/osgeo/ticket/190 and
http://wiki.osgeo.org/wiki/Postgrey
If postgrey is not the right solution, it's easy to revert back to the original config by,
Editing /etc/postfix/main.cf and comment out lines 222 - 236
smtpd_recipient_restrictions = permit_mynetworks,
permit_sasl_authenticated,
reject_invalid_hostname,
reject_non_fqdn_hostname,
reject_non_fqdn_sender,
reject_unauth_destination,
reject_unknown_recipient_domain,
reject_unauth_pipelining,
reject_unauth_destination,
#reject_rbl_client list.dsbl.org,
#reject_rbl_client sbl.spamhaus.org,
#reject_rbl_client zen.spamhaus.org,
#reject_rbl_client lists.spam.sux.com,
check_policy_service unix:postgrey/socket,
permit
Restart Postfix
$ sudo /sbin/service postfix restart
cheers,
shawn