There are a lot of email list verification services to choose from.
BriteVerify is another one.
BriteVerify lets you upload a list of email addresses to verify, and does a fine job verifying them. That's all it does, as opposed to many other similar services who have other features as well, like email guessers and email finders, and other things.
If you're looking for a simple service that is focused on just email verifications, then BriteVerify may be a good option, if you can handle the above average pricing.