Mailboxlayer

Mailboxlayer's JSON API verifies email addresses through SMTP checks, syntax validation, and mailbox existence probing. It catches common typos, identifies disposable email providers, and flags risky addresses before they land in your database.

The platform appeals to developers who need a simple REST API they can call from their stack. Response times are quick (usually under a second), and the free tier lets you test the service before committing to a paid plan.