[Dovecot] related, but off-topic: how to allow users to change password?

My dovecot is currently configured to authenticate vs. a userdb/passdb passwd-file that contains, for each user:

username:passhash:5000:5000::/path/to/home::userdb_mail=/path/to/maildir Is it possible to let users authenticate and change their passwords? There are some webmail client add-ons that allow such things if users are system accounts or in a MySQL/LDAP db. Does anyone else use passdb/userdb passwd-files like above and have a method for allowing users to change their passwords from the web?

Sorry for the slightly off-topic question, but hoping another Dovecot admin has solved this problem. Preference is to not to be tied to any particular webmail client just for this change password feature.