Within Activity Monitor the Exchange Store items Scanned value remains at 0, indicating that no items are being scanned.
First seen in
PureMessage for Microsoft Exchange
PureMessage uses Exchange Web Services to scan the information store and this requires the Exchange Autodiscover service to be correctly configured. This issue is caused due to the Exchange Autodiscover service not being configured correctly.
What To Do
Follow the instructions in the below Microsoft article:
Configure Exchange ActiveSync Autodiscover Settings