In Office 365, you’ll use their “Connection Filter” options:

  1. Sign into Office 365 and click “Admin” > “Admin Centers” > “Exchange
  2. Under the “Protection” list, choose “Connection Filter
  3. Click the “Pencil Icon” to edit
  4. Choose “Connection Filtering” on the left side menu
  5. Click the plus “+” symbol and add the first IP and click “OK“(find our current IP addresses for whitelisting here.)
  6. Repeat Step 5 to add our second IP address.
  7. Check the “Enable Safe List” checkbox, if necessary
  8. Hit Save