It might be possible that you want to send a cookie along with a service callout. You can add a Transport Header action to your callout to add a header but I found out that you can’t just input a String in there. You have to insert a cookie-values fragment. You can accomplish it by doing this.
Next select the ‘Add header’ button and select ‘http’ and ‘Cookie’. Now select the ‘Set header to’ radiobutton and input a variable here for example. Mine is called NatCookie here. But how should your variable look like? The XML should look like this:
If you execute the service call you can see it filled the cookie filled with your value in the $outbound: