scriptuser ALL=(ALL) NOPASSWD: /usr/sbin/postfix
scriptuser ALL=(ALL) NOPASSWD: /usr/sbin/dovecot

$ /usr/sbin/postfix
postfix: error: to submit mail, use the Postfix sendmail command
postfix: fatal: the postfix command is reserved for the superuser
$ /usr/sbin/dovecot
Fatal: open(/var/run/dovecot/master.pid) failed: Permission denied