Pre paid courier service between mumbai and houston?

Can just put an envelope in a envelope and post it through the local post office using International Air track & trace which takes 5-11 working days to destiantion, or a slower means is international Economy through the post office which takes 11-23 days to destination. Talk with your local post office on options, fedex and dhl are priority service providers and are slightly dearer, post is the cheapiest option.