When a user registers he gets an activation email

I'd like the user to see in this activation email his account details (username & password)

I know how to let him see his username

All I need to to do is to go to:

language/english/mail_template/register.php

And edit this file

The {X_UNAME} stands for his username

But what stands for his password?!

I tried {X_PASSWORD} and {X_CODE} but none of them worked

Anyone knows how do I let the user see his password too in the activation email and not just his username?!