You can only apply this if you are hosting your own Exalate app for ServiceNow. If you are not and you need this, please contact Exalate support.
This article describes how to send custom headers from the Exalate app for ServiceNow to the ServiceNow instance.
Set custom headers in an environment variable
Add the custom headers to the following ServiceNow environment variable
2. Start up your ServiceNow instance
3. Run the synchronization as usual. Now requests include the custom headers you've set.