Okay, I agree, your way is better. Let's make it as simple as possible:

HELO shrek.org 250 smtp.aol.com Hello shrek.org [123.45.6.7], glad to see you. MAIL FROM:news@shrek.org 250 news@shrek.org... Sender ok RCPT TO:ogre@aol.com 250 ogre@aol.com... Recipient ok VERP FROM:ogre-aol.com-1007679391-1f04c30dabd-news@shrek.org 250 ogre-aol.com-1007679391-1f04c30dabd-news@shrek.org... Sender ok RCPT TO:witch@aol.com 250 witch@aol.com... Recipient ok VERP FROM:witch-aol.com-1007679391-297c0dd13a3-news@shrek.org 250 witch-aol.com-1007679391-297c0dd13a3-news@shrek.org... Sender ok DATA

The way it's already implemented in Postfix is:

MAIL FROM: sender@sender.dom XVERP

everything else is as normal, but the envelopes get VERPed.