Block emails from an email in Microsoft Office 365

 You can create a mail flow rule to block the sender’s email address in the new Exchange admin center. Here are the steps:

1. Sign in to the new Exchange admin center at https://admin.exchange.microsoft.com/
2. Go to Mail flow > Rules
3. Click + to create a new rule
4. In the New rule page that opens, enter a name for the rule
5. Under Apply this rule if, select The sender…
6. Select is this person and enter the email address of the sender you want to block
7. Under Do the following, select Block the message
8. Click Save to save the new rule