mailcow

The Courier mail transfer agent (MTA) is an integrated mail/groupware server based on open commodity protocols, such as ESMTP, IMAP, POP3, LDAP, SSL, and HTTP. Courier provides ESMTP, IMAP, POP3, webmail, and mailing list services within a single, consistent, framework. Individual components can be enabled or disabled at will. The Courier mail server now implements basic web-based calendaring and scheduling services integrated in the webmail module. Advanced groupware calendaring services will follow soon. The Courier mail server's source code should compile on most POSIX-based operating systems based on Linux, and BSD-derived kernels. The Courier mail server should also compile on Solaris and AIX, with some help from Sun's or IBM's freeware add-on tools for their respective operating systems. The Courier mail server evolved out of several related projects, that merged together (more on that later). The Courier mail server implements SMTP extensions for mailing list management.

You can have a fully functional mail server installed in a few minutes, mostly waiting for scripts to do the work. The whole package is designed with reasonable defaults to get you up and running quickly, without having to know the internals and without making decisions that could break the email system. User data and configuration is strictly separated from binaries. User database is stored in SQLite database - in file. This makes Poste.io fully compatible with external storage. Migration, backups or updates are therefore very easy and mostly consist of files manipulation. Poste.io has been built from the ground up with security in mind. Internet history is littered with painful security incidents, so we traded old email client compatibility and insecure authentication methods for features that meet today's for features that meet modern security requirements.