According to a recent aricle by Boomerang featured on Mashable on.mash.to/yC6wlT, to get people to read non-marketing emails, the best times to send such emails are 5-7am and 11am-1pm.
To get responses to email use the following words: apply, opportunity, demo, connect, payments, conference and cancellation. Avoid the following words: confirm, join, assistance, speaker, press, social and invite.