Hi Amanda, I'm working with a couple of customers right now on this very issue--we've found that you need to target the prospect with a specific question / need / want that they have as defined in your Customer Journey or Marketing Funnel. This is really hard to do! But if the email comes from a Sales Rep and has some specified information relating to an expressed interest from the prospect then you'll see much better results. Let's say it is a Pet and Training Tradeshow: you can ask to set up a time for a personal meeting to talk about your "specific dog training needs" or "learn the best techniques to teach your dog to come 100% when off leash"!
Just some ideas . .
-Vanessa