Fully featured mail server

What makes up a mail server and what services do most organisations expect from their self hosted server.

Organisations need to send and receive emails, as a minimum you need SMTP to send and receive email and IMAP for users to manage their email.

SMTP - Simple Mail Transfer Protocol

Transferring email from one place to another is the responsibility of a Message Transfer Agent (MTA), also known as a mail transfer agent or mail relay.

There are many MTAs, with sendmail one of the earliest. The one chosen at Persistent Objects is Exim as it's highly configurable  with extensive facilities, its configuration is straightforward, is open source and available for almost every Linux and Unix distribution.

Exim https://exim.org/

Internet Message Access Protocol (IMAP)

Designed in 1986, IMAP is the standard for users to manage their email, it's available on almost every device from mobiles to desktops and is also used by CRM software and corporate systems to manage emails.

One of the benefits of IMAP is simultaneously managing emails on mobiles, desktops and webmail.

Other services

Address books and calendars

Most people have address books and calendars, by maintaining a central service based on industry standards CalDAV and CardDAV users can keep the same lists on their mobiles and desktops.

Radicale https://radicale.org/

Mailing list service

Mailing lists are invaluable for managing subscriptions. Even the simplest of lists benefit from automating common tasks subscribing and unsubscribing users, showing archives and preventing abuse.

Sympa https://sympa.org