Can you remember life before email?
It's an amazing thing how interconnected we have become -- sending and receiving messages instantaneously from people all over the planet.
The problem with email is that we think that in hitting the "send" button we have communicated our message, when in fact, many times, if not most of the time, we have not.
Like George Bernard Shaw said, The greatest problem with communication is the illusion that it has taken place.
It's not your job to state your case so much as it is your job to make sure your audience understands your message. Without the nonverbal cues face-to-face communication provides, it's more challenging to know whether or not you're getting your message across with email. And probably most of your messages rely on this medium.
What you want to do is overcommunicate. Students who get good grades know this; they overstudy to make sure they do well on the assignments.
This makes it really difficult to vilify the recalcitrant consumer. It's not that they're stupid, it's that you didn't explain it very well.
In your activities today, remember to overcommunicate. It will save you time, money, frustration, effort down the road.