The last I looked I had nearly 1100 legitimate contacts in my outlook address book and the majority of them have all the details filled out. Prior to my Beta testing I had a serious spam situation and thank god to Hector Santos over at Santronics It is under control (more to follow later still locked into a NDA) But I can not imagine sending a verification e-mail to all those in my address book on a periodic basis to make sure the e-mail account is still valid.
With using the same e-mail account over the past 6 years I am sure people know where to find me and since we have eliminated 99.9% of the spam before it hits outlook life is good. But if you like to keep your address book cleaned up here are a couple of services that ZDNet reviewed. [ZDNet]