No solution.
Passwords are hashed into the database.
No way they can be unhashed.
As of Mambo 4.5.1 by default the initial password is not included in the first welcome email ([DETAILS]).
Its mostly a Joomla/Mambo issue.
That's why if you forget your password the system assigns a random new one - the reason is because the system does not know it!
Security is much better this way.