Jeff,
Their feeling does have an impact on the interpretation of your e-mail, but I have found that the tone and wording are more important. If I am warm and clear in my email the student is less likely to read it the wrong way. When I get in a hurry and just respond with the hard facts, I usually get responses about how insensitive I am. It is a fine line at times and sometimes I fail at it. Although the more I do it, the better I get.
Herbert Brown III