mail pouch vs pouch

mail pouch and pouch both are nouns.

Word	Noun	Adjective	Verb	Adverb
mail pouch	Yes	No	No	No
pouch	Yes	No	Yes	No

As nouns, pouch is a hypernym of mail pouch; that is, pouch is a word with a broader meaning than mail pouch:

mail pouch (noun)	pouch (noun)
pouch used in the shipment of mail	a small or medium size container for holding or carrying things
	(anatomy) saclike structure in any of various animals (as a marsupial or gopher or pelican)
	an enclosed space

mail pouch (verb)	pouch (verb)
	swell or protrude outwards
	put into a small bag
	send by special mail that goes through diplomatic channels