makesmtpaccess rebuilds the contents of the /usr/local/etc/courier/smtpaccess.dat database from the contents of the files in the /usr/local/etc/courier/smtpaccess directory. When the esmtpd script starts couriertcpd, the script specifies /usr/local/etc/courier/smtpaccess.dat file to control access to Courier's ESMTP server daemon. The makesmtpaccess script must be run before any changes in the /usr/local/etc/courier/smtpaccess directory take effect.
See the manual page for couriertcpd for information on the format of the access files.
The default Courier configuration uses the same access file, /usr/local/etc/courier/smtpaccess.dat for both the regular ESMTP server, and the message submission server on port 587 (RFC 2476). It is possible to use different access files. To do so, create a different access file, edit /usr/local/etc/courier/esmtpd-msa, and set ACCESSFILE to the filename of the access file directory (the directory containing the plain text files, not the .dat file). Then, use makesmtpaccess-msa instead of makesmtpaccess to build the .dat file.