A reason to use the hyphen when electronic mail is meant. Scripps-Howard word list
says "email" is French for a color, a moderate greenish-blue to bluish green
Often used in cloissoné.

cloissoné
adj.
5Fr, lit., partitioned < cloison, partition < VL *clausio < L clausus: see CLOSE16 designating or of a kind of enamel work in which the surface decoration is set in hollows formed by thin strips of wire welded to a metal plate
n.
cloisonné enamel