If I enable the "droponconnect" option I see the 518 message when testing via Telnet and the session is dropped but if I send mail normally and the connection is dropped I do not receive a NDR??  Do I not have this setup incorrectly or is this the way that ORFilter is designed. 

Without a NDR I was forced to disable this option ensuring legitimate mail is not dropped.  I allow the users to determine what is kept and what is discarded but would prefer to drop on connect as that is more efficient.