Not sure if I’m giving away some good trick here, but I thought I’d shared my experience with this add on for gmail. Once installed, Boomerang allows you to schedule emails to be sent at a given time and date, using gmail. You compose your email normally, but there’s an extra button “Send later” through which you can control the timing.
I think it’s quite cool $-$ you can actually write emails at 11am and then send them out very late at night or really early in the morning, so that the recipients will go: “wow! This guy is really working very hard… Look at what time he’s replied to my email!”
Then again, since XY has arrived, it is very likely that emails sent out from my account at 6am or late at night have actually just been written…