The decent thing to do is to try as much as possible to avoid piquing their self-esteem. It's impolite to start an email with the main topic you want to discuss, and when I feel the need for a buffer, I generally talk about the weather or current events. I do not add subjective views when I do that - I don't say it's depressing because of the continual rain or the freezing cold. I make it a rule to write only the facts. I might say I'm writing this email in a room where it's starting to get warmer after the rain and ask how the recipient is doing, that the clock has just struck noon or there is a full moon in the sky. None of these words have much meaning to them, but they're only greetings. I think it's nice to avoid stimulating the recipient needlessly at the beginning of an email.