qmail 1.03 with many common patches, including QMAILQUEUE. courier-imap (1.4?) vpopmail 5.2.1 Squirrelmail 1.4 MySQL support for both vpopmail and squirrelmail Spamassassin and CLAM AV
That might be too much detail, but I wondered if the MySQL support would be an issue. Please link me to wherever I can find a description of this SMTP denial support.