This is where you make or break yourself. You HAVE to use a service that supports responsive coding and helps provide it or you'll just make yourself certifiably nuts. Forget sending through your gmail or outlook or hotmail account....or directly via your domain email.
Check these companies out
- MailChimp (Our favorite)
- Campaign Monitor
- Get Response
They all have some fairly user-friendly capabilities and if you have a geeky staff member who can utilize photoshop (or similar) and has some minimal knowledge of html coding, then you can do it on your own.