Jolene,
Great topic! I spoke on this at a show in my previous role. Most emails are read from a mobile devices now. This means two things...1) you have to catch their attention in the preview of the push notification 2) end the email with a way that allows for an easy to type response either accepting your request or denying it. Don't be afraid of a "no".
Example: Customer Name, Jolene here with ABC. I have some news I think would be interesting to you. Do you have 10 minutes for a call when you get off work today?
Your customer will see "Customer Name, Jolene here with ABC. I have some news" and at least read it. At that point they can email you a quick response like "yes, call after 5:30".
How we end our conversations can dramatically effect our results. I have full intentions on replying to emails but in some cases I open them while out and never get back to them because it doesn't allow for a quick response. I simply forget.
Hope this helps! I found it works great for me.