I don't know about blocking, but you can have them
automatically deleted by using the Rules Wizard.
Go to Tools > Rules Wizard. Click the New button and
follow the prompts. Outlook will allow you to specify
the criteria that distinguishes the unwanted e-mails, and
then what should be done with them (e.g. automatically
delete).
Get mailwasher, it is free and easy to use. When the person keeps getting
bounced mails he/she might give up bugging you, (that is of course if they
are bugging you)