mail boat vs packet

mail boat and packet both are nouns.

Word	Noun	Adjective	Verb	Adverb
mail boat	Yes	No	No	No
packet	Yes	No	No	No

As nouns, mail boat and packet are synonyms defined as:

Other synonyms of mail boat include mailboat, packet boat.

mail boat (noun)	packet (noun)
a boat for carrying mail	a small package or bundle
	a boat for carrying mail
	(computer science) a message or message fragment
	a collection of things wrapped or boxed together