Guide to Unix/Explanations/Mail Server Overview/Outgoing mail
Outgoing mail is first written to a spool directory on the client machine[edit | edit source]
Outgoing mail produced by the mail client is first written to a spool directory.
Mail Submission Agent[edit | edit source]
The mail submission agent takes mail from the spool directory and forwards this to the listening mail transport agent on the mail server via SMTP.
Delivery[edit | edit source]
The mail transport agent forwards the mail to the internet service providers SMTP server for delivery or delivers the mail directly if the recipient is local.
A copy is placed in the sent items folder[edit | edit source]
The mail transport agent places a copy of the mail into the users sent items folder on the mail server.