HI May-ye
No, it cannot call third-party API interfaces. At least not yet.
The current API support of AsyncOS is limited to reports querying, tracking, and quarantining data. Additional details can be found in the following links.
AsyncOS API (cisco.com)
Cisco Secure Email Gateway - Programming Guides - Cisco
Since you want to integrate a 3rd party sandbox service with your Cisco Secure Email solution, I would suggest taking a look into the SecureX documentation, and also its orchestrator. I am pretty sure you can integrate both solutions via SecureX, since it can talk to any product with API support.
Cisco SecureX – A Simplified Security Experience - Cisco
Regards,
Andres
