Sometimes, some phishing spam go through the Anti Spam filter, and to avoid these senders to be able to keep bothering other internal users, we need to add them to our antispam filter as blocked.
The first thing we need to do is going to www.security.microsoft.com then click on Policies & rules
Then click on Threat policies
Click on Anti-spam
Click on Anti-spam inbound policy (Default)
After you click, this windows will open, scroll down and click Edit allowed and blocked senders and domains
Then the following windows appear, click on Manage () Sender(s)
Then click on Add senders
Then write the sender’s email address and press enter, then click the button Add senders, then click Done and click Save.
After all these steps, you’re done.