Since $snmp is now declared private, I can no longer create an smtp class & plug it in. Therefore I no longer have access to the $smtp->do_verp. Unable to use VERP on out going mail. Declaring $snmp as public (as it was once) will fix this. However, class.smtp.php on line 542 uses a string of "XVERP". This does not work with Postfix. Changing the string to " XVERP" (note the leading space) fixes the problem.