GetMyeBayDetails api doesn't return 'DHL Global Mail' shipping carrier but can I still use it in CompleteSale api ?
Yes, you can use 'DHL Global Mail' carrier in the CompleteSale api.
This is what you should specify in the request : <ShippingCarrierUsed>DHL Global Mail</ShippingCarrierUsed>
Please be informed that our engineering team is currently working on it, so this information may not be available in the api docs or in GetMyeBayDetails api response yet.