Urgent! same password for everybody?

hello,
when users create a new account on my site the email that is sent out look like this see below. But for some reason the password is same for every new user.

Any ideas why?

Hi [yaymail_customer_username],

Your account has been created automatically, please use the login details below.

Your username: [yaymail_customer_username]
Your password: [yaymail_user_new_password]
 
You can access your account area to view payments, change your password and more at our homepage by clicking Login [yaymail_user_account_url]