Mailtrap

Mailtrap started as a testing tool and expanded into a production delivery service. The free tier covers 4000 emails per month and emphasizes reliability for transactional mail like order confirmations and password resets. You get SMTP and API access, event tracking, and detailed logs so you can see exactly what's happening with each send.

Mailtrap suits developers shipping low-volume transactional email who want production infrastructure without choosing between a testing sandbox and a live service. The free tier is enough for small apps; growth requires a paid upgrade, but the foundation is there and the service is transparent about what you're getting.