Is there any way in JIRA REST API to know if an issue was created by JIRA Mail Handler?

I am working on a ScriptRunner script to perform some post-processing (on “Issue Created” event). Ideally, I would like to execute the script only for issues created by Mail Handler. However, from the JSON response returned by the REST API, I don’t see any issue attribute that can confirm if the issue was created by the Mail handler or not.