Self-hosted Communication - Email - Mail Delivery Agents software

Mail Delivery Agents (MDAs) - IMAP/POP3 server software.

3 apps, ranked by GitHub stars weighted by maintenance health.

Dovecot

IMAP and POP3 server written primarily with security in mind.

Actively maintained ★ 1.3k MIT, LGPL-2.1 ~$3.5/mo

DavMail

POP/IMAP/SMTP/Caldav/Carddav/LDAP exchange gateway allowing users to use any mail/calendar client with an Exchange server, even from the internet or behind a firewall through Outlook Web Access.

Actively maintained ★ 774 GPL-2.0 ~$10/mo

Cyrus IMAP

Email (IMAP/POP3), contacts and calendar server.

Actively maintained ★ 653 BSD-3-Clause-Attribution ~$3.5/mo