1. Login to 365

    1a. Open Exchange Admin Center - Mail Flow - Rules

2. Select to create Rule, name something similar to "Exempt (email address) from Clutter"

3. Follow the format above. Be sure to set the message header to: 'X-MS-Exchange-Organization-BypassClutter' with the value 'true'

4. Emails from the sender should now no longer forward anyone's Clutter folder.