ManyMail Sandbox SMTP is an open-source project designed for developers to self-host a mail server for testing purposes. It offers features like concurrent SSL, TLS, and unauthenticated servers, a web interface for reading emails, and an API for programmatic email management.

Build, Share, and Test HTML Emails.

Mailtrap provides a RESTful email infrastructure API with high deliverability rates, an email sandbox for safe testing, and actionable analytics. It offers SDKs for smooth integration and supports both transactional sending and bulk email delivery.