An email landed in my mailbox recently. It was from a person whose name I didn't recognise, and the subject was very short. In gmail the body is displayed after the subject, and the mail appeared like this (names and subject have been blurred to project the innocent!):
Obviously there's a something at the top left of the email which lets you ignore the email. It happened to be the "alt text" on an unscubscribe button. But in the email list it looks like it's telling me off!
So just a warning if you're setting up email newsletters - include some nice friendly text at the top or as the "alt" text for the first image, and Google won't present your email the way this one was presented.