I received a mail from you asking for my account data including the password - is it genuine?

No. We will never ever ask you to tell us your password.

This mail is from someone trying to steal and abuse your account. This kind of attack is called phishing.

Can you change my login shell to bash ?

No, sorry.

The recommended login shell is zsh, and tcsh is available for those who really want it badly. Users with those login shells will find identical environments after they login. This is important to make documentation universally valid, for example. Unfortunately, bash is so limited in functionality regarding processing of startup files that this cannot be achieved, hence we can't provide it as a login shell. There are no other limitations to using bash - you're free to use it for scripts as well as interactively. Most users giving zsh a chance soon find that it's very similar to bash and has a number of useful additional features.

How can I delete ~/.OldFiles ? It's eating my quota!

No, it isn't. That's just a snapshot of your home directory as of last night. It doesn't count towards your home quota.