Suppose, I have set auto-forward emails in my Gmail or other service providers to some other email ID. What kind of SMTP headers are inserted in that email so that the receiver SMTP server of those email realizes that these are auto forwarded email?
I believe this header should also help in avoiding recursive looping between 2 email servers.
[Note: It's observed that for auto forwards, Gmail sends "to:" header in the beginning in SMTP message MAIL with a suffix called "_caf".
e.g. xxx@gmail.com will be xxx+caf_=other=somedomain@gmail.com.]