Read your email, don't read into it
Itzy Sabo has written a little piece on one of my pet subjects tone in email. His post Don’t write to me in that tone of voice! highlights a study finding that if you make a guess as to the tone half the time you will be wrong.
Said it before and if I end up dying before email does then I'm sure I'll say it on my death bed: "read your email, don't read into it".
If you're not sure whether someone is trying to convey a tone you will find out in your next verbal or physical interaction.