Spacing between lines during composing message

I’m looking for adjusting general spacing between lines while composing e-mail. We’ve moved from Postbox to eM Client (trying out now) and in Postbox there was more spacing available. We want to add a bit more spacing between the lines in our e-mail. How can I do that?

There is an eM Client Sleekplan request to change line spacing, so suggest to vote for that.