Configure Outbound Filtering for Mesh in Office 365/Exchange Admin

This guide outlines how to create an outbound connector in Microsoft 365 in order to facilitate the routing of outgoing email through Mesh.

We recommend you consult Microsoft’s official documentation to ensure the setup is relevant to your environment.

Using Exclaimer? Please use this guide instead →

Connector Setup

Step 1: Connectors page

Navigate to the “Connectors” page on your Exchange Admin Console.

Step 2: Add a connector

Select “Add a connector”.

Step 3: Specify mail flow

Select “Office 365” under the “Connection From” option. Select “Partner organization” under the “Connection to” option.

Step 4: Connector name

Give the connector a name and optionally a description. Ensure the “Turn it on” box is checked.

Step 5: Use of connector

Select the “Only when I have a transport rule set up that redirects messages to this connector” option.

Step 6: Routing

Select “Route email through these smart hosts”.

Enter the smart host specific to your region.

Step 7: Security restrictions

Select “Always use Transport Layer Security (TLS) to secure the connection” and “Issued by a trusted certificate authority (CA)”.

Step 8: Validate connector

The next step will present a validation screen.

For an outbound connector, the email address should be external to the tenant being configured. If the testing email address is internal, Microsoft 365 will not use the smarthost.

The most important aspect here is the connection to the smarthost successful.

Step 9: Review connector

Review the details you have entered and click save. Your connector list will now be updated to reflect the change.

Transport/Mail Flow Rule Setup

Step 1: Rules page

Navigate to the “Mail Flow” section in your Exchange Admin Center and select “Rules”.

Step 2: Create a new rule

Click “Add a rule” and then “Create a new rule”.

Step 3: Rule conditions

Give the rule a name and apply the following rule conditions.

The sender is external/internal → Inside the organization.
The recipient is external/internal → Outside the organization.
Redirect the message to → the following connector → select the Mesh Outbound connector you created.

Step 4: Exceptions

If you need to add exceptions to emails that should not pass through our smarthost, the “Except If” condition facilitates this.

For example, if configuring an autoforward, please consult our Outbound Smarthost guide to check if this step may be necessary. Outbound Smarthost | Auto-Forward

Step 5: Set rules settings

Ensure the “Enforce” is selected.

Step 6: Review and Finish

Review the details you have entered are correct.

You’re all set.