Fast, scalable, enterprise mail/groupware server providing ESMTP, IMAP, POP3, webmail, mailing list, basic web-based calendaring and scheduling services.

GPL-3.0

Exim

Message transfer agent (MTA) developed at the University of Cambridge.

GPL-3.0

Apprise

Apprise allows you to send a notification to almost all of the most popular notification services available to us today such as: Telegram, Discord, Slack, Amazon SNS, Gotify, etc.

MIT

Python

Asterisk

Easy to use but advanced IP PBX system, VoIP gateway and conference server.

GPL-2.0

Continuwuity

Community-driven Matrix homeserver, the continuation of conduwuit focusing on user experience and new features (fork of Conduit).

Apache-2.0

Rust

Dovecot

IMAP and POP3 server written primarily with security in mind.

MIT

LGPL-2.1