To block an email address or sender in Outlook, you have to follow these steps carefully. 

Open your Outlook email client

In your inbox or the folder containing the email you want to block, locate the email from the sender you wish to block.

Right-click the email from that sender.

Find Junk or Junk Email

Then select block sender

And click confirm

That's it.

In case issues then visit: https://emailspedia.com/how-to-block-an-email-on-outlook