My friend is using a service called SpamArrest
to manage his unruly inbox. Any new senders will receive an email back from the server asking they pass a "capcha" type non-robot test. After that, they're whitelisted and may email freely.
He's moved to Office 365 and SpamArrest isn't compatible.
The goal is a robust email whitelisting cloud service that will work with O365 Exchange and Outlook Desktop Client. Do you know of a product that can meet this need?