[USER=265]@eddyshaf[/USER]
Here's a little insight from a long-term customer follow-up perspective that might help you.
Letting go of an email lead is hard to do, but it might be your best long-term strategy.
Many people may have 2-3 email accounts and the email they gave you may be the email they use for promotional sign-ups and they are not actively checking it.
Although it may seem like it's not that big of a deal to keep emailing inactive/ghost leads, the problem is their lack of engagement can impact the deliverability of your other emails.
Here's a great Returnpath article that explains this issue:
6 Reasons to Treat Inactive Subscribers Like Zombies
http://blog.returnpath.com/blog/casey-swanton/6-reasons-to-treat-inactive-subscribers-like-zombies#sthash.X70Hz2Tc.dpuf
We create customer newsletters for dealers and for salespeople. I frequently get asked if we can send the customer newsletter to their prospect list which includes lots of inactive emails. Many are surprised that we want nothing to do with prospect emails. The reason for this is that newsletter engagement with prospects is typically very low while their spam complaint rates are very high.
Which makes sense.
If I log into my throw-away email account once a month to track down the Bed, Bath and Beyond coupon I need, and see a newsletter from a dealer that I sent a vehicle inquiry to over a year ago, I'm very likely to mark it as spam since I have no relationship with them and I'm not in the market anymore.
My advice from a long-term email deliverability perspective would be to cut off your ghost leads if they have never been active after a certain period of time.
Additionally, removing the ghost leads should make your metrics more meaningful since you will now be measuring your effectiveness with those leads that have had some time of engagement.