Postfix - Postfix is a mail transfer agent (MTA) that routes and delivers electronic mail.
Talend - Talend Cloud delivers a single, open platform for data integration across cloud and on-premises environments. Put more data to work for your business faster with Talend.
mailcow - An open source mailserver suite.
Talend Data Integration - Talend offers open source middleware solutions that address big data integration, data management and application integration needs for businesses of all sizes.
Mail-in-a-box - Mail-in-a-Box provides webmail and an IMAP/SMTP server for use with mobile devices and desktop mail software and also includes contacts and calendar synchronization.
Matillion - Matillion is a cloud-based data integration software.