I know about iOS device UDID and that are case-sensitive. But I have a query, my client sent me all upper case in UDID characters. I have never seen any upper case letters in UDID's. I don't find any document that says UDID can have upper case letters consists. I need to create a right build to them. Could someone advise, what should I ask my client now? I can't say them, UDID is incorrect. Can I ask them to make sure the case-sensitive and send me back? Also, Can UDID have upper and lower case combination in letters?

Thank you!