Excuse me while I guffaw at this:
The results from this study suggest there is a relationship between typeface selection and the reader’s perception of an email. The email presented in the typeface that was judged in previous studies to be low in appropriateness for email (Gigi) was perceived to be less stable, less practical, more rebellious, and more youthful than either Calibri (highly appropriate) or Comic Sans (moderately appropriate). This finding suggests that documents presented in typefaces that are viewed as less appropriate are seen as less serious and less professional in nature. The appropriateness of the typeface also affected the perception of the email author in that the email using Gigi created a perception of an author who is less professional, less trustworthy, and less mature. Finally, the typeface that was lower in appropriateness led participants to conclude that the author was a lower level trainee employee. When choosing a typeface for a document, the level of appropriateness should be taken into account in order to avoid sending unintentional messages.
Apart from the question of what there could possibly be on God’s green earth for which Comic Sans is “moderately appropriate,” I plan to ignore this entirely; anything you get from me will be in your mail client’s default typeface because I think HTML-encoded mail is an abomination unto the Lord and a pain in the ass generally. With the exception of one monthly newsletter which is sent to me as a Word document (which I open in OpenOffice.org because I refuse to install Microsloth Office), I read everything in plain text; if nothing else, it creates the illusion of less spam.