New User Verification eMails Disappear

OK, so I was running version 7.00.07, but some users on the site were saying they were not receiving the verification eMails after they registered. So a few days ago, I updated to 7.01.02, and I am having this same problem. Quite a few users have registered on the site, have received eMails, and can login, but there are a few users who never receive a verification eMail... why is it some people never receive this mail? What is the cause? Better yet, what is the fix?

It sure would be nice if there was better user management in future versions. Since updating to 7.01.02, the UCC (User Control Center) Infusion will no longer work correctly for me, and this was the only thing which shown un-activated users, and gave me an easy option to activate or delete them... as it stands now, I have users who say they never received an eMail, all I can do is assume Fusion is waiting for them to register and waiting to drop them after 24 hours, but since I have no way of seeing a list of such users, I am only guessing who tried to register.... anyways, off subject.

Why are some of my users not receiving this eMail?? I am having more and more people come to me saying the verification was never received, and they are unable, even after numerous registration attempts, to receive the eMail. Where is it disappearing? Any help on shedding some light on this would be greatly appreciated... because I have no clue what is going on here.