IndiMail - Messaging Server for Allhttps://github.com/mbhangui/indimail-virtualdomains/wiki/IndiMail
A Fast, Efficient & Secure Mail Server with Multi-Domain/Multi-Host support
IndiMail is a Scalable, Secure, Reliable, Efficient, and a highly configurable Messaging Solution. Most of the parameters are configurable through set of environment variables or control files. Using a system called 'envrules', these variables are configurable on a per-user basis allowing IndiMail to behave differently for different users (or set of users). The system IDs and configuration files used by IndiMail are all configurable through a set of environment variables, allowing you to customize IndiMail at run time the way you want.
IndiMail has the ability to distribute the users in a domain across multiple hosts. You can have multiple hosts hosting a domain placed anywhere and tied up by IndiMail. This does not force a filesystem architecture like NFS to be used for have large number of users (typically in an ISP/MSP environment)
IndiMail has multiple queues (called a queue collection). IndiMail's multiple queue eliminate what is known as the 'Silly qmail syndrome'.
IndiMail supports all protocols required in a messaging server - SMTP, ESMTP, QMTP, QMQP, IMAP, POP3.