Headers of responded emails of meeting.

Hii team,

I am trying to filter out the email which is coming as meeting response like accepted,decline or maybe on the basis of headers. The catch is if someone replied with the gmail account then I am getting auto:submitted header. But if he is exchange user then I am not getting this header. Irrespective of the platform(google,exchange) from where I created the meeting. Then in those case how can i filter out those emails, Is there any specific header for that kind of emails?