How to block email ID in 0365

In the Microsoft 365 Defender portal 

Go to Policies & rules 

> Threat Policies > Rules section > Tenant Allow/Block Lists. Or, to go directly to the Tenant Allow/Block List page

On the Tenant Allow/Block List page, verify that the Domains & addresses tab is selected.
 

On the Domains & addresses tab, click 
 

Block.

In the Block domains & addresses flyout that appears, configure the following settings:

Domains & addresses: Enter one email address or domain per line, up to a maximum of 20.

Remove block entry after: The default value is 30 days, but you can select from the following values:

• 1 day
• 7 days
• 30 days
• Never expire
• Specific date: The maximum value is 90 days from today.

Optional note: Enter descriptive text for the entries.

When you're finished, click Add.