Guerrilla Mail vs Sendinblue

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.

Sendinblue rebranded to Brevo in 2023, and its REST API still covers the same ground under the new name: transactional and marketing email, SMS, and contact/campaign management behind an API-key header. A free plan covers a daily email allowance before metered and subscription paid tiers.