The Verifalia API provides an email validation service to integrate in existing applications. It features a complete syntactical engine, role account detection, and disposable address detection. This RESTful API responds in JSON format, and authentication occurs in "HTTP Basic Auth". The Verifalia API is built by Cobisi which offers software development tools for the .NET platform.
Free plan (with no credit card required) with up to 125 free email validations per day, unique support for International Domain Names and Mailboxes, different levels of quality and features to choose from (to meet your needs and budget), simple RESTful HTTPS API with free and open source SDKs for Microsoft .NET and Ruby.