I've purchased a couple email validators, but this one is the one I am keeping.

The limits are plenty generous for my needs, I am seeing a high level of accuracy and the AP is FAST. Most of my traffic is real-time, via various forms, so dependability and speed in the API is critical for me. The one list that I sanitized came back with results that are comparable to the other tools, so no complaints there either, even though I probably won't use that much.

I've got it hooked up so that all my contact forms, surveys, and quizzes run through Verimail, and so far things are working flawlessly. Mailable addresses get added to my CRM and mailing software. Unmailable addresses do not. Pretty much everything I could wish for in email verification.