On Windows 7 (or Vista) I use
Real-time API for Bulk Email Verifier (2016/04/29 16:23)
Based on queries of our customers, we have implemented Bulk Email Verifier API. The API is very simple to integrate into a web site regardless the platform. The API allows you to create larger tasks and thus verify large database of emails, but it also supports a real-time verification of a single address, that can be used in registration forms. The real-time version is guaranteed to provide an answer within 20 seconds, and has an average verification time below 10 seconds. For the full description and code samples, please see the linked API documentation.