Dovecot
IMAP and POP3 server written primarily with security in mind.
Homepage
Source code
Other self-hosted communication - email - mail delivery agents
Email (IMAP/POP3), contacts and calendar server.
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.
Run it with Docker
Spin up Dovecot on a VPS in minutes. Use the docker-compose generator to get a starter snippet, or grab a server below.