The following steps must be completed before routing outbound email from Office 365 to Proofpoint;

1. Allow Proofpoint to accept outbound email from Office 365 - read more 

2. Update SPF Record to include Proofpoint - read more

Create Outbound Connector in Office 365

  1. Sign-In to the O365 365 Admin portal.
  2. Click on Admin > Exchange.

This will launch Exchange Admin Center

  1. Click Mail Flow > Connectors.
  2. Click + to access menu.
  3. For “From” select “Office 365”.
  4. For “To” select “Partner Organization”.
  5. Click Next.
  6. Enter a value for Name (e.g.“Proofpoint Essentials”).
  7. Enter a value for Description (e.g.“Route outbound email via Proofpoint").
  8. You will turn this outbound connector on once you are ready to cutover mailflow.
  9. Click Next.
  10. For “When do you want to use this connector?” select “Only when email messages are sent to these domains”.
  11. Click +.
  12. Enter * to specify all domains.
  13. Click OK.
  14. Click Next.
  15. For “How do you want to route email messages?“ select “Route email through these smart hosts”.
  16. Click + and enter your Proofpoint smart host value 
    (US:, EU:
  17. Click Save.
  18. Click Next.
  19. For “How should Office 365 connect to your partner organization's email server?” choose your preferred approach.
    • If you choose “Always use Transport Layer Security (TLS) to secure the connection”, please choose  “Any digital certificate, including self-signed certificates“.
  20. Click Next.
  21. Click Next.
  22. Click + icon and enter an email address for validation.
  23. Click OK.
  24. Click Validate.
  25. Click Save.