If you want to stop receiving email from someone, you can add his or her email address to your blocked senders list. Outlook automatically moves any new mail that you receive from this person to the Junk email folder. When you want to receive mail from this person again, you can remove his or her email address or domain from your blocked senders list.
Block a sender
In the message list, select a message from the sender whom you want to block.
In the Outlook menu bar select Message > Junk Mail > Block Sender.
Outlook adds the sender's email address to the blocked senders list.
Note: You can restore any of the mail that is in the Junk email folder. Click the message that you want to move to the Inbox folder, and then on the Home tab, click Junk, and then click Not Junk.
Unblock a sender on non-Exchange based accounts
In the Outlook menu bar select Tools >Junk Email Preferences.
Note: If Junk Email Preferences is grayed out your account may be hosted by Exchange. See Unblock a sender on Exchange based accounts below
On the Blocked Senders tab, select the email address or domain you want to unblock, and choose Remove the selected sender button .
Unblock a sender on Exchange based accounts
Exchange accounts, like Outlook.com or your work email account hosted by Exchange, do not have access to the Junk Mail Preferences. For those accounts junk mail filtering is handled on the Exchange server and is not a client option. To remove a blocked sender, see Block or allow (junk email settings).