Yep, "Why should you update Poser" really reads just like "Why you should stop eating these 4 foods" in an email title. It is not alarmist to just come right out and say what you mean. Especially considering you may be (probably are) dealing with people who don't have English as their native language, and even among "Englishes" there is plenty of room for ambiguity.

Be blunt. Like a baseball bat. Or a cricket bat. Or something else blunt :)