If you are thinking about ingesting Proofpoint TAP logs into Splunk, then it may be possible.
You can use Proofpoint modular inputs over there.
Here is the link for the Proofpoint TAP Add-on: https://splunkbase.splunk.com/app/3681/
You need principal and secret for API call
Example Commands In Curl
The following commands assume that principal and secret are defined environment variables. They correspond to the service principal and secret that was created on the Settings page.
curl "https://tap-api-v2.proofpoint.com/v2/siem/issues?format=json&sinceTime=2016-05-01T12:00:00Z" --user "$PRINCIPAL:$SECRET" -s
Retrieves events from noon on 05/01/2016 to the present. Returned events are limited to just permitted clicks and delivered attachment threats. Output is in the JSON format.
curl "https://tap-api-v2.proofpoint.com/v2/siem/all?format=syslog&sinceSeconds=3600" --user "$PRINCIPAL:$SECRET" -s
Retrieves events to the present, starting 3600 seconds before the query time. All events are returned. Output is in the syslog Format.
curl "https://tap-api-v2.proofpoint.com/v2/siem/clicks/permitted?format=syslog&interval=PT30M/2016-05-01T12:30:00Z" --user "$PRINCIPAL:$SECRET" -s
Retrieves events from the thirty minutes beginning at noon UTC on 05-01-2016 and ending at 12:30pm UTC. Only permitted clicks are returned. Output is in the syslog format.
curl "https://tap-api-v2.proofpoint.com/v2/siem/all?format=json&interval=PT30M/2016-05-01T12:30:00Z&threatStatus=falsePositive&threatStatus=active&threatStatus=cleared" --user "$PRINCIPAL:$SECRET" -s
Retrieves events from the thirty minutes beginning at noon UTC on 05-01-2016 and ending at 12:30pm UTC. All events are returned. False positives are included in the output. Output is in the JSON format.
For more help , you can visit https://help.proofpoint.com/Threat_Insight_Dashboard/API_Documentation/SIEM_API
If you want the filter and MTA logs from your Protection server you will also want to add your Splunk server to the remote log server settings located in: Logs and Reports > Log Settings in Protection.
After configuring pps and receiving data:
Data input -> Proofpoint TAP SIEM Modular Input
Siem url host=tap-api-v2.proofpoint.com
index (we were limited in choices for some reason, which caused us to update the macro set up in pps config)