MSN privacy

[NJOK]

On signing into hotmail, for added privacy, you can select 'Always ask for my email address and password' so that your email address doesn't appear automatically the next time someone goes to sign in.
However, if you are in messenger and click to read your emails, the next time you visit hotmail, your MSN/hotmail username is in the sign-in box.

If it possible to stop this happening?