I am wondering if there is an app for Proofpoint or is it ingested via the TA-SMTP-Reputation that is included with the Microsoft Exchange app? Once the TA is setup properly of course.
To determine if there is an app for any technology, search on http://apps.splunk.com
The TA-SMTP-Reputation included as part of the Microsoft Exchange app is for checking your reputation, not others. As a result, it doesn't know anything about ProofPoint.
Proofpoint now has a beta app that will allow you report on and visualze your Proofpoint Protection Server and TAP data! Check out the new app here:
Be sure to follow the instructions listed in the details to get all the needed TA's etc that the app needs to work correctly.