Open Outlook
Select the email from the sender you want to block
Right-click the message
Choose Junk
Select Block Sender
Confirm the action if prompted
Open Outlook on the web
Select the email from the sender you want to block
Click the More actions menu
Choose Block
Confirm if prompted
Open Outlook
Go to Settings
Select Mail
Choose Junk email
Add the sender’s email address or domain to the blocked senders list
Save the changes