The most important that real users will read this letters and take attention to e-mail distribution. Many people now do not read e-mal and cmc because there are a lot of spam their.
A lot depends are really users which receive cmc are interested in the cryptocurrency and the services that are promoted. If they are interested in them they can pay attention to advertising.
Promotion is necessary in all the cases and it is necessary to have different kind of promotion including email distribution via CMC database and other kinds, because everything is important and necessary for promotion.