
Description: OpenSMTPD is an open source SMTP server daemon for Linux and BSD operating systems. It aims to be a free, secure, and featureful SMTP server for both hosting providers and end users.
Type: Open Source Test Automation Framework
Founded: 2011
Primary Use: Mobile app testing automation
Supported Platforms: iOS, Android, Windows

Description: Exim is an open source mail transfer agent (MTA) developed for use on Unix systems. It is lightweight, flexible, and one of the most popular MTAs for Linux and BSD systems. Exim aims to be secure, scalable, and easy to configure.
Type: Cloud-based Test Automation Platform
Founded: 2015
Primary Use: Web, mobile, and API testing
Supported Platforms: Web, iOS, Android, API