You must enter your email address in the From: field. You should also set your email address for all identities, so that you do not have to enter it for each message.
Jo moatte jo e- postadres yn it Fan: - fjild ynfiere. Jo moatte ek jo e- postadres foar al jo identiteiten ynstelle, sadat jo it net foar elts berjocht hoege te dwaan.