OpenSMTPD

Secure SMTP server implementation from the OpenBSD project.

Communication ISC C deb

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Asterisk

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

Communication GPL-2.0 C deb

6/5/2026 Details →

Courier MTA

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

Communication GPL-3.0 C deb

6/5/2026 Details →

Dovecot

IMAP and POP3 server written primarily with security in mind.

Communication MIT LGPL-2.1 C deb

6/5/2026 Details →

Exim

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

Communication GPL-3.0 C deb

6/5/2026 Details →

Kamailio

Modular SIP server (registrar/proxy/router/etc).

Communication GPL-2.0 C deb

6/5/2026 Details →

ngircd

Portable and lightweight Internet Relay Chat server for small or private networks.

Communication GPL-2.0 C deb

6/5/2026 Details →