Hi gramesh
The Bulk folder is in fact meant for all those spam!!
Don't Worry about that. It will not add up to your account storage space.
They will be cleared every month by default.
If it is annoying you you can set in options to clear it every day or every week.
For that go to Mail Options -> Spam Protection ->
In Spam Filter
set the option
Immediately delete these messages upon receipt. (Note: If you choose this option, you will not be able to review the messages before they are deleted.)
That's it
Regards