I am sending quite a few emails from coda and that works pretty well. Logo’s, links, boldface can be used and are incorporated in the emails my recipients receive.
But the layout leaves to be desired: column layouts are lost, but you can use table layouts instead. But tables in email layouts have a problem: when you setup your tables without headers and without gridlines, it looks OK in Coda, but in the sent email the header are still there, the gridlines become separation lines (horizontal) and around the headers there is a darker, solid line.
If these table issues could be fixed, we could send a lot nicer emails.