Assume that your recipient gets a ton of email and that his or her inbox looks like rush hour.
Assume that approximately 50% of emails are read on smartphones, so keep your emails short and sweet.Assume 1 in 3 persons read their emails on their smartphones, so keep your subject line to no more than 45 characters (6 to 10 words).
Assume you recipient is busy so you need to attract his attention with subject lines that are direct and that convey as much information as possible succinctly, so your recipient knows what to expect when he or she opens it.
Assume, that as Israelis, our default communication style is direct. However, in other parts of the world, they expect a more indirect style. So soften and pad your language.
Consider participating in the "Get to the Point" Email Workshop/Lecture.