Perhaps you don't want to install the whole qmail rpm
# wget http://repo.qmailtoaster.com/8/spl/sqlmd/mariadb/testing/x86_64/qmail-1.03-3.3.7.qt.md.el8.x86_64.rpm
List all packages in .rpm file
# rpm -lqp qmail-1.03-3.3.7.qt.md.el8.x86_64.rpm
# rpm -lqp qmail-1.03-3.3.9.qt.md.el8.x86_64.rpm |grep qmail-s
/var/qmail/bin/qmail-send
/var/qmail/bin/qmail-showctl
/var/qmail/bin/qmail-smtpd
/var/qmail/bin/qmail-start
/var/qmail/man/cat5/qmail-spamt.0.bz2
/var/qmail/man/cat5/qmail-spamthrottle.0.bz2
/var/qmail/man/cat8/qmail-send.0.bz2
/var/qmail/man/cat8/qmail-showctl.0.bz2
/var/qmail/man/cat8/qmail-smtpd.0.bz2
/var/qmail/man/cat8/qmail-start.0.bz2
/var/qmail/man/man5/qmail-spamt.5.bz2
/var/qmail/man/man5/qmail-spamthrottle.5.bz2
/var/qmail/man/man8/qmail-send.8.bz2
/var/qmail/man/man8/qmail-showctl.8.bz2
/var/qmail/man/man8/qmail-smtpd.8.bz2
/var/qmail/man/man8/qmail-start.8.bz2
# rpm2cpio qmail-1.03-3.3.7.qt.md.el8.x86_64.rpm | cpio -iv --to-stdout ./var/qmail/bin/qmail-smtpd > /tmp/qmail-smtpd
# qmailctl stop
# mv /var/qmail/bin/qmail-smtpd /var/qmail/bin/qmail-smtpd.bak
# mv /tmp/qmail-smtpd /var/qmail/bin
# chmod +x /var/qmail/bin/qmail-smtpd
# chown root:qmail /var/qmail/bin/qmail-smtpd