While you can't prevent someone from sending a message to you, you can block up to 500 email addresses or web sites. All incoming messages from these blocked addresses will be automatically deleted, without bouncing back to the sender or going into one of your mail folders.To block an address:
Business Email Options Link
Business Email Options Pull-Down Menu
Business Email Blocked Addresses Link
Business Email Add Address to Blocked Addresses.
To remove or unblock an address or domain from your list:
Business Email - Remove Email Address from Blocked List