Mk,
Open Outlook Express and then:
If you don't get any genuine newsletters from Microsoft, click Tools,
Message Rules,
Mail, then on the 'message rules' panel click 'new' to create a new rule and
enter the name Microsoft in the blocked senders, and choose the delete from
server option. Click 'ok'. and 'ok' again.
If you do get genuine MS email, then I noticed that the subject headers stay
the same for a day or two. So enter the header in a new rule, then update it
till this whole thing stops. You'll know as soon as a new header gets
introduced, no problem.
Hope this helps,
Chek