If emails from a sender no longer arrive in your inbox, the sender may have been blocked. This is how to remove the block.
Outlook (classic)
In the ribbon, open Home › Junk › Junk E-mail Options …. In the simplified ribbon, it is under … › Block.
Go to the Blocked Senders tab.
Select the address, click Remove and confirm with OK.
New Outlook and Outlook on the web
Open Settings (gear) › Mail › Junk email.
Under Blocked senders and domains, click the trash icon next to the address.
Click Save.
Tip: To make sure emails from a sender never land in the junk folder, add the address under Safe senders.