There is absolutely a way to do this. I run the engineering team at Kickbox. Our product takes a list of emails and will tell you which are valid and which are not (without sending to them). We have an API too.
You want to avoid bounces by sending to bad emails. Send to too many and your IP address will be globally blacklisted.
You can technically verify emails yourself through regular SMTP (just stop the SMTP commands before actually sending the email), but there are plenty of weird SMTP edge cases and for any serious number of emails you'll want to do this through a proper email network (like ours :-).
Hope that helps