VERP and DKIM in mail

Hello,
Can anyone please give me some idea about VERP and DKIM regarding the mailing system? Actually my problem was basically of tracking the bounced mails from the mailing list fired from my site.
Previously the return-path wasnt coming out correctly from my live server. Then i found out it was because of the VERP service that was turned on in my mail server. So, i requested them to turn it off. Now the return-path s are coming out correctly. I’d request you to have a look at this thread of mine to get the basic idea of what i was up to (http://www.sitepoint.com/forums/showthread.php?p=4475123#post4475123) especially the first and the last thread.
But still the system cannot track the bounced mails. I dont know why. But the demo server can. The “full headers” (“view original”) as comes in my mail from the live and the demo server, has only one major difference in it. In the live one, there’s an added property called DKIM-Signature and X-Thread-Info. But the demo hasnt one. I suspect it may have something to do with redirecting the bounced mails to where i want.
There lies my problem. Can anyone please confirm me that whether it’s because of what i suspect or not…

Thanks in advance,
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