The Courier authentication library will serve our purpose by separating the user authentication from the OS X user administration into a standalone user administration based on a MySQL database. You can find the software and documentation from the Courier authentication library web-site. Check the blog for the latest supported version.

Extract the source archive in a directory, open a Terminal session, change the directory to the one you extracted the archive in and type in the following commands as a normal user (please note that the configure command will run for quite some time):

export MACOSX_DEPLOYMENT_TARGET=10.5
./configure --with-authmysql \
--without-authpam \
--with-mysql-libs=/usr/local/mysql/lib/mysql \
--with-mysql-includes=/usr/local/mysql/include/mysql

Followed by:
make

Issue the install command when the compilation has finished:

sudo make install

If you are building a fresh installation run the following command to create new configuration files. Do not run it if you are just upgrading to a new version.

sudo make install-configure

Next step: Building the Courier IMAP/POP3 Server