mailing-card vs postcard

mailing-card and postcard both are nouns.

Word	Noun	Adjective	Verb	Adverb
mailing-card	Yes	No	No	No
postcard	Yes	No	No	No

As nouns, mailing-card and postcard are synonyms defined as:

mailing-card and postcard: a card for sending messages by post without an envelope

Other synonyms of mailing-card include post card, postal card.

mailing-card (noun)	postcard (noun)
a card for sending messages by post without an envelope	a card for sending messages by post without an envelope