I have a rule of thumb that when I send an email, I make sure that if it’s viewed on a smartphone, you can get through it in a few swipes. In my experience, if it’s longer, people start assuming, “Wow, this is a book. I’ll read this later.” And how often do they actually return to finish reading your tome? Not often. That’s how emails fall through the cracks.
There are people in this business who get more than 100 emails a day. If you don’t get through immediately, they aren’t going to remember you later. In order to get your message across effectively, it needs to be less than a hundred words. In fact, your best bet is limiting yourself to three to five sentences. When you commit to being concise and compelling, people appreciate your brevity.
I recommend checking out three.sentenc.es, which can be used as part of your email signature block to let people know why your messages are so brief, even curt. This service is also available for two, four or five sentence emails as well. Who knows? If other people see that shorter emails are catching on and start emulating them, that would definitely be a good thing for everyone.