Oh hey, maybe the Summary Reports will work for you? Under Organization > Monitor > Summary report you can view the summary report for your MX network. In that report is the Top N blocked sites shown a few different ways: You can set these reports up to be emailed to you every day/week/month etc. It's not real-time alerting to blocked URLs, but you can see every day what was blocked the previous day in an email to your inbox.
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