If you have given clients your e-mail address, then you must expect them to use it. Some people are more comfortable with e-mail than anything else, I know I am. I'd much rather e-mail than call.
I guess I'm out voted. I'll think about it.
Personally, I think email is good when there is no rush. No transcription errors when a client emails me amounts. (I tell them not to send me Social Insurance Numbers and other private info by unencrypted email. Very few of my clients are able to send encrypted email.)
If I were cancelling an appointment, I would do it by email, if the appointment was at least several hours away. I would phone if I didn't get a reply a couple of hours before the appointment.
If my business needed an e-mail account, I would set one up at Google (Gmail) for it and keep that one open during business hours so I could check it frequently.
I have an email address for biz that uses my domain name. It forwards to Gmail and it is always open. I just don't sit at my computer the whole time I'm working. I also get into a "zone" while working at the computer and might not check more than once every two hours.