Review on MailboxValidator by Tutcht Cobb

I've been using it for several years now, mostly because we have hundreds of thousands of emails in our database that need cleaning at least once per year or so - this tool does just what you want.

No complaints here! It's very fast (and free) compared with other tools out there; if your list has more than 100K records then they might be able to speed things along even further by offering some paid features but honestly those are not needed most times unless you're dealing with really large databases. We do bulk cleansing every few months/years as part of our regular data maintenance processes which includes removal of dead people from mailing lists etc.