The command "esmtpd start" runs couriertcpd in the background, listening on the SMTP port. couriertcpd will run courieresmtpd in response to connection requests.
The command "esmtpd stop" stops the couriertcpd daemon, shutting down the ESMTP service.
The command "esmtpd-msa start" starts the server on the message submission port, port 587. "esmtpd-msa stop" stops it. The difference between esmtpd and esmtpd-msa is that the latter is set up for additional processing as defined by RFC 2476 (mainly that the messages will have the Message-ID: and Date: headers added, by default).
Normally, makesmtpaccess(8) automatically runs "esmtpd restart", in order to reread the /usr/local/courier/etc/smtpaccess.dat access file, so you don't have to do it manually, yourself. Similarly, makesmtpaccess-msa(8) automatically runs esmtpd-msa restart
This configuration file initializes various settings for courieresmtpd.
This configuration file initializes the settings for courieresmtpd when invoked by esmtpd-msa. Note that this file is used to override the settings /usr/local/courier/etc/esmtpd. The command "esmtpd-msa start" first reads /usr/local/courier/etc/esmtpd, then afterwards /usr/local/courier/etc/esmtpd-msa. Any settings in esmtpd-msa override the corresponding settings in esmtpd