The following article contains instruction on how to block an unsafe message sender and remove an address from the block sender list.
How to Block A Sender:
1. Open the message of the sender you wish to block.
2. Within the ribbon, select the drop down arrow on the Junk button.
3. Select the option, Block Sender.
Note: An alternate way is to simply right click the message, Select Junk Mail and then Block the Sender.
How to remove an address that has been blocked:
1. Open your Outlook 2011 Client.
2. Along the navigation pane, select tools, then Junk E-mail Protection.
3. Click the Block Senders tab.
4. Locate the address you wish to unblock and remove the address.
5. Select OK when finished.