Creating fast and effective emails is the creativity itself. Your email should be short enough to be powerful but long enough to justify it to you. The length and style of your e-mail copy should be personalized to the needs of your audience or product offering.
Shorter emails are more likely to receive attention and replies than longer emails. People reading have too much to figure out before you grab their attention and gain their trust with a few words; they're likely to ignore the post instead of reading the whole email.