How to set hourly outgoing email limit by number of recipients in Exchange admin center?

Step 1: Sign into Office 365 admin portal via https://portal.office.com

Step 2: Click on Admin from the left pane and navigate to Security center.

Step 3; Now navigate to Threat Management > Policy > Anti-spam settings.

Step 4: Expand Outbound spam filter policy ‎(always ON)‎ and click on Edit policy.

Step 5: Expand Recipient Limits section and enter the recipient limit in the Internal and External hourly limit boxes.

Step 6: Click Save.