Integration with Smarsh archiving is a feature of Brosix Enterprise.
You will need to have an account with Smarsh to receive the Users Activity Log from Brosix. Then go to Web Control Panel -> Settings -> Integrations tab. Find the “Smarsh archiving” section and activate the feature.
Once activated, this feature will automatically transfer all your User Activity Logs to Smarsh. Records will still be available on Brosix servers for your review and you will still be able to download the monthly archives from Brosix Control Panel.
You can find here more details about Brosix Users Activity Log feature