But if you use it incorrectly, your customers will still call you. And the number one reason why your customers will still call you, even after you've sent out an email telling them that this year you're going to schedule by email is:
Failure to respond to their email.
When someone sends you an email, they really don't know if you received it. Maybe it got lost in cyberspace, maybe it ended up in your junk mail folder, maybe you just missed it. So the most important thing that you can do that will encourage your customers to use email, and discourage them from calling you is to
Respond to their email.
Your response doesn't have to be elaborate. Just a quick *Thank you* will do. Personally, I like to write *Cool, got it*, or some such casual message like that, because it's the way I talk.
I conduct a lot of business through email. I've done a lot of cartoon illustrations for humor writer Rambling Russ (that's him being attacked by bees), all through email communication. But one day I picked up the phone just to chat with him. It's nice to hear voices.