Can my users change their own email password?
Yes, to do so, copy the link for your email control panel. It will look like:
https://SOME_PHPWEBHOSTING_SERVER_HERE.phpwebhosting.com/cgi-bin/qmailadmin/
Have them login as their username (instead of postmaster)
and then click:
“Edit existing address: pop3”
and it will allow them to change their own password.