Concepts
- see here
- Mail Transfer Agent (MTA) transfers emails between clients and server via SMTP e.g. Postfix
- Mail Delivery Agent (MDA) sorts incoming mails on the local computer to the right mail boxes e.g. Dovecot
- Mail User Agent (MUA) is a end-user mail programm
- IMAP server delivers content of mail boxes
- Relay sends mails on behalf of someone else e.g. google for ubuntu home PC