Password encryption

I have 2 users whom i have password as 'Chinatown1'. 
But both have totally different encrypted passwords in SQL table
'UserObject'

How is the encrypted password created in the first place. I have a need 
where i need to send emails only to users with a particular password.

Do***ent says , it uses first 4 characters from the password as the salt. 
But how is it done for a new password.
-- 
Regards