While voice is the interaction type most preferred by customers, it is gradually losing ground to other channels. After voice, email is by far the most dominant channel delivering interactions into the contact center. Many businesses have imagined that email support would be a great way to eliminate costly phone calls, but relatively few have been able to provide a truly remarkable customer experience via email.
E-mail really can and does add value to a lot of customers, but too often the contact center fails to capitalize on its full potential. In a world of "instant answers", few customers are interested in waiting 24 to 48 hours for a response. Unless email is the ONLY option given the customer, that kind of turnaround is guaranteed to have him picking up the phone to call. People don't typically expect 30-second responses via email, but you need to do better than a 24-hour service level. Email won't have the same aggressive service level that accompanies phone calls, but they also can't be treated as "we'll get to them when we get to them." Emails need to be explicitly managed and staffed or else customers will refuse to use it.
Don't encourage email if the customer has a complicated story to tell. If the customer can't ask the question in a few sentences, it's probably going to be too complex to resolve via email. Email volleys back and forth are annoying and time-consuming. You can't always avoid this from happening, but do your best to cut it short if you can. (If there's a complicated email and the customer provides a phone number, it's often better to pick up the phone and try to resolve it with a call.)
Email can become a disaster if the customer decides to call in before their previous email is answered. In the best case, it's a waste of time. One agent handles the call and another agent ends up answering again in email form. You HOPE both agents give the same answer. If not, you'll have a real time-wasting mess on your hands. You can be sure there is no "moment of truth" to be found in that quagmire.