Postfix architecture is modular and contains different daemons each specifically handling only a few tasks. The most important daemons are the following: master is the main daemon that starts all the other daemons. smtpd is the SMTP server daemon handling incoming connections to receive emails from another mail server or client. smtp is the SMTP client handling outgoing connections to send email out to another mail server. local is the local delivery agent responsible for delivering email to the local server. qmgr processes and controls all messages in the mail queue. Maps are used in postfix to control email routing. Such maps are used to accept or reject email, inform postfix about local recipients and more. The main configuration files are main.cf which is the global configuration for all daemons and the master.cf which defines the runtime environment for the daemons. The master.cf configuration thereby overrides the configuration options from the main.cf. Lets Secure
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