Topic 108 · Essential System Services
108.3 Mail Transfer Agent (MTA) basics
Step 1 of 11 · weight 3
MUA and MTA
This objective is not a full mail-server build. It is the transfer layer: who writes the message, who accepts it, and who delivers it.
- MUA is the program the user writes, sends, and reads with. mail, mailx, and mutt are MUAs
- MTA is the background service that accepts, routes, and tries to deliver. Postfix, Exim, and Sendmail are MTAs
- mail is the MUA. Acceptance, routing, and delivery happen in the MTA behind it
Exam note
Weight 3. mail and mailx are not MTAs. Logging stayed in 108.2.