If you want to find the password for  email account’s  in plesk then there are 3 ways to get the email account’s password ::

1>   To find password for a single email  account

root@server[#] /usr/local/psa/bin/mail --info info@domain.com

2> To find all email account passwords for a single domain

root@server[#] /usr/local/psa/admin/bin/mail_auth_view | grep domain.com

3>    The below command will list passwords for all email accounts in plesk.

root@server[#] /usr/local/psa/admin/bin/mail_auth_view

OR

root@server[#]mysql -uadmin -p` cat /etc/psa/.psa.shadow`


http://www.linuxspy.info/1783/find-email-account-password-in-plesk/