Based on Revision 59 of original libopensmtpd at http://imperialat.at/dev/libopensmtpd/

INSTALLING on Fedora

# Make sure these are installed first: make gcc mandoc

sudo dnf install make gcc mandoc

make -f Makefile.gnu

sudo make -f Makefile.gnu install

# You can remove rpms you installed: sudo dnf erase make gcc mandoc