IT Pro: Setup Hybrid mail flow to route through Exchange on-premises

This step-by-step guide is intended only for Exchange Administrator, IT Administrator, and Microsoft 365 Administrator.

Microsoft 365 and Exchange server Hybrid environment with Centralized Mail Transport(CMT) enabled.
All Outbound emails of On-prem and exchange online users must route through Exchange on-premise.

Exchange online user's outbound emails are routed through Microsoft Online Protection(EOP) instead of through local exchange on-premises after you configure Xink server-side (Xink-rerouting).

Configure Outbound and Xink handled emails to go through exchange on-premises by creating a new connector and a transport rule.

Step 1 - Create new Outbound Connector

1. Sign in to your Microsoft 365 admin center.
2. Go to Mail flow > connectors tab.
3. Create a new Outbound connector to route Xink-Handheld messages to exchange OnPrem (see image below)

Step 2 - Create a new transport rule that routes Xink-Handheld emails to Exchange on-prem environment.

Note: Since the problem is only affecting X-Xink-Handled messages then you must apply this new mail transport rule limited to X-Xink-Handled only.

  1. In the Exchange admin center (Microsoft 365), go to mail flow > rules.
  2. Click the + button and select Create a new rule.
  3. Once the wizard opens, click More options (lower-left corner) to see all available settings.
  4. Name your rule e.g 'FromXink-to-onPremises'
  5. Select: A message header > includes any of these words > specify header name to X-Xink-Handled and the value to Yes.
  6. Add the following action: Modify the message properties > set a message header to X-Goto-OnPremises and the value to Yes.
  7. Click add action and choose: Redirect the message to > the following connector. Select the Outbound connector you previously created e.g 'XinkOut-to-on-Premises'.
  8. Click add an exception to add the following exception: A message header > includes any of these words.
    Set the header name to X-Goto-OnPremises and the value to Yes. and Finally, click the Save button.

    Now all messages that are routed through Xink Server-side will be sent back to your local Exchange environment and Centralized Mail Transport configuration will send out the messages to its recipient. 

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