I think that each organization/campaign has specific criteria for generating the voter lists they use, and most provide some information on their website about how they choose to target voters.

I know it's annoying to get unneeded reminders! I often get election day phone calls even after I have already voted early. But voter lists are never going to be perfect. I think with any effort on this scale there are going to be a small percentage of names on their lists that aren't good matches, for various reasons.