HTC mail not showing notification

[psxindo]

I'm using unrooted mytouch 4g.

My email has been showing in the notification bar whenever I receive a new mail.
But since 4-5 days ago, it doesn't show any notification. This only happen to my hotmail/msn account. my other email is fine.

Is this a problem with hotmail or the mail app?
And how to fix?

Thanks