Plesk email users often get their passwords lost.
Fortunately Parallels has implemented a command to see all passwords for all users in all domains:
`/usr/local/psa/admin/bin/mail_auth_view`
You can filter the output to see one account password (quotes must exist):
`/usr/local/psa/admin/bin/mail_auth_view | grep "johnsmith@domain.tld"`
Also you could get statistical information about how many email accounts supports your server:
`/usr/local/psa/admin/bin/mail_auth_view | wc -l`
As the result you get the total amount of email accounts in you server for all the domains, of course, you could filter by domain:
`/usr/local/psa/admin/bin/mail_auth_view | grep "domain.tld" | wc -l`
And all the variations you can imagine.