Guerrilla Mail vs mailboxlayer

Guerrilla Mail issues disposable, auto-expiring inboxes and lets a client poll or fetch their incoming messages through a simple JSON-over-AJAX endpoint, no signup or key required. It's a fully free anti-spam utility with no paid tier.

A REST service from APILayer that checks whether an email address is syntactically valid, resolves to real DNS/MX records, and flags free or disposable providers in one call. Free for light personal use, with paid tiers for higher volume.