Email Commando is your solution! This software works great with ANY size list, big or small.  The Commando will quickly scan a list of emails and weed out the ones that are no longer working for any reason.  These reasons may include "user no longer exists", "domain doesn't exist" and many more. The software is very fast, can set up to 100 threads, and use proxies. Valid (as well as invalid) addresses are saved in a text file.