Before you do the build, make sure you run niscript (as root) to properly create a postfix user, and postfix & maildrop groups. DO NOT USE THE MULTIPLE USERS APPLICATION TO CREATE THE POSTFIX USER! 1) su 2) ./niscript this creates the necessary users & groups for proper operation of postfix 3) ./stash-sendmail move your existing sendmail binaries somewhere safe 4) make install When the script asks you for setgid (the default will be no) tell it maildrop 5) edit /etc/postfix/main.cf to suit your requirements 6) postfix start 7) Test. Read INSTALL for a series of suggested tests. 8) cp -R darwin-Postfix /System/Library/StartupItems/Postfix 9) edit /System/Library/StartupItems/Sendmail. add "exit 0" as the first line