Don't rely on e-mail to communicate emotion

"We tend to misinterpret positive e-mail messages as more neutral, and neutral ones as more negative, than the sender intended. Even jokes are rated as less funny by recipients than by senders."

--Daniel Goleman, author of Social Intelligence, writing in the New York Times

So what's the solution? There are many, but here's one: Don't rely solely on e-mail when emotion is involved, either yours or your reader's. Writing has many advantages, but in short, quickly written pieces it's not  good at conveying subtle shades of feeling.