Optionally download and install the Courier™
Authentication Library from http://www.courier-mta.org/authlib/, in
order to use LDAP, MySQL, or PostgreSQL based mail
authentication.
Follow the instructions in the INSTALL file to compile and install maildrop from source. If you are using an RPM-based Linux distribution, see the README file for instructions on building binary RPMs.
Download maildrop: http://www.courier-mta.org/download.html#maildrop