The qpasswd tools are meant for use with checkpassword-compatible
authentication programs like qmail-popup and qmail-smtpd. Currently, the
following auth mechanisms are supported: plain, login, apop, cram-md5,
cram-sha1, cram-ripemd, and digest-md5. The tools:

- multicheckpw (runs multiple checkpassword programs)

- checkqpasswd (for virtual users)

- checkpasswd (for system users in /etc/passwd)