Components of a typical mail server edit
A typical Unix mail server installation consists of the following components:
Incoming Mail edit
Incoming mail is delivered to one or more internet POP3 mailboxes. The Mail Server retrieves the incoming email and stores it in local inboxes to read by the client mail reader.
Outgoing Mail edit
Outgoing mail messages, whether destined for local or outbound delivery are sent to the Mail Server. The Mail Server determines whether the destination address is local or outbound. Local mail is treated as incoming mail and processed as above. Outbound mail is delivered via SMTP to an Internet mail server for forwarding to its final destination. The Mail Server stores a copy of the message in the sent items area.
Local Mail edit
Local mail, for example mail generated by a notification daemon, is delivered directly to the Mail Server. The Mail Server also stores this mail in the local inboxes to read by the client mail reader.
Client Connectivity edit
The Mail Server provides IMAP Services. A client can view the incoming messages by connecting to the IMAP services.
The Mail Client can instruct the mail server to mark messages as read, or move them from the Inbox to a local folder on the Mail Server.
Messages composed by a Mail Client are relayed to the Mail Server for delivery to recipients.