We've been taught in school to write beautiful long letters full of politeness. So, we assumed the same applied to electronic mail, as we're also communicating in writing, only the medium is a bit different. Well, I've recently come to the conclusion that the best thing to do is the exact opposite - keep e-mails short as can be.
Because I saw this comic:
And I wondered - what kind of e-mails do I prefer receiving? The shorties! Because I instantly know what's going on. And writing? Shorties too, of course. And I'm not the only one, apparently, as someone got quoted a lot recently for twittering:
my secret time saving email tip: change your desktop email signature to "Sent from iPhone" - then write 1 sentence replies! sshhh
Okay, so I prefer getting shorter e-mails, but does everyone? Professors, customers, strangers usually expect some more politeness than a "yes" or "no". But think of that person... he/she's most probably struggling with an overloaded inbox and will appreciate if you respect her/his time. Plus, if you use the little cheat above, you will suggest that you answered the e-mail as soon as you could, even if you weren't at your computer. Still, I'd consider a single word as rude, but bottom-line, there is a huge difference between e-mail and snail mail, and less is more.