Message Routing - Enhanced Connection Filtering

This article contains information on configuring Enhanced Filtering for Connectors in Mimecast, including considerations, steps to configure in the Microsoft Defender Portal, and adding Mimecast IP ranges to improve email security and delivery efficiency.

Overview

Mimecast works with Microsoft to enhance messaging security, and in addition to the Microsoft default Connection Filtering policy, your enterprise license may have access to Enhanced Connection Filtering. If you choose this method instead of the standard, please inform yourself of the considerations segment below.

Considerations

Careful consideration should be given to using Enhanced Connection Filtering. Below are examples of checks still performed by Microsoft when using this method, which will likely increase admin overhead.

• • • Microsoft will continue to perform Spam checks.
    • Microsoft will continue to perform RBL (Real-time BlockList) checks.
    • Microsoft will continue to perform DNS (Domain Name Services) checks.

For example, messages passing through or held and then released by Mimecast may still get held by your Microsoft, which is not the case when using Standard Connection Filtering for inbound delivery routing.

Configuring Enhanced Filtering for Connectors

For full details, see the Microsoft article here on how this functions and how to configure this feature.  An outline of the steps required is also provided below.

Enhanced Filtering for Connectors requires an inbound (receive) connector to be configured in the Exchange Admin Center, if one is not present already.

You can configure enhanced filtering for Connectors, by using the following steps:

1. In the Defender Portal, expand Email & Collaboration in the sidebar on the left.
2. Navigate to Policies & Rules | Threat Policies | Rules section | Enhanced Filtering. 
3. Select the connector you want to configure on the Enhanced Filter for Connectors page.
4. Configure the following setting:

• • • • Skip these IP addresses that are associated with the connector
      • Add the Mimecast IP Ranges. See Data Centers & URLs.

5. Click on Save.

See Also...

• • • Email Security Cloud Gateway - Inbound Delivery Routing For Microsoft 365