You can easily block specific senders within Outlook. The easiest method is to right click on the email from the sender you want to block and select Junk from the menu, then choose “Block Sender”. This will add that email address to your Blocked Senders list.
You can also add or manage your Blocked Senders list within Outlook by clicking on the Home tab along the top, then select Junk and finally select Junk Email Options. In the window that opens, you will see a tab named Blocked Senders. Clicking on this tab will allow you to add the specific email to be blocked. You can also edit or remove any addresses or domains that had previously been blocked.
Note: There is a limit of 500 addresses that can be added to the Blocked Senders list. EOP will only process the first 500 addresses in the Blocked Senders list. Addresses added over that limit may still be filtered by Outlook Junk Mail rules but will not be filtered by EOP at the server level. A Blocked Sender list greatly exceeding the 500 address limit may result in spam filtering not working properly or at all, so it is highly recommended to keep this list below this limit.