Alternatively, if you're only looking for the threat data from their Targeted Attack Protection service, there's the following APIs:
https://help.proofpoint.com/Threat_Insight_Dashboard/API_Documentation/SIEM_API
https://help.proofpoint.com/Threat_Insight_Dashboard/API_Documentation/Campaign_API
https://help.proofpoint.com/Threat_Insight_Dashboard/API_Documentation/Forensics_API
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