Email takes a lot of time. This problem gets the most pervasive in case of people who write a lot of e-mails as more e-mails sent cause lots of replies and the conversation goes on. Long e-mails tend to take long to respond building up a queue. Treat e-mail like instant messages. My solution is to count number of lines wrapping around and keeping it short to one paragraph of three lines for most of e-mails. Occasional long e-mails take up to three paragraphs. Keeping most of the e-mails up to five sentences typically work best.