Would be good to setup a system where you are able to get people to label something as urgent and you would still get this otherwise you would see it when you wanted. Depending on who is sending the majority of email your way and your social relationships this could work well.
Yeah it depends on who is emailing you. For Harj it is probably startups/ investors/ press etc, where there can be some social pressure upon using some kind of urgent tag only when it is genuinely urgent.
If most of your emails are customers who always want service right now then it is going to be a bit different.