mailboat vs packet

mailboat and packet both are nouns.

Word	Noun	Adjective	Verb	Adverb
mailboat	Yes	No	No	No
packet	Yes	No	No	No

As nouns, mailboat and packet are synonyms defined as:

Other synonyms of mailboat include mail boat, packet boat.

mailboat (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