There's really no way to do this properly because using e-mail for everything is totally amateur hour. E-mail is a push medium so it requires every sender to figure out where to send things. Worse, it creates multiple versions of every message so that it creates the problem of figuring out which version is the latest or even valid one. (Not to mention all those gigabtyes of power point presentations cc'd to the whole company.)

The cool kids use pull medium where stuff is put up on some form of bulletin board and it's only up to all the receivers to decide what they want to look at: which they have to do anyway. Things like "this guy is on vacation" problems don't happen anymore. There's only one latest version of everything and the valid one is the one with the "approved" checkmark on it. Also, since they're internal (although usually cloud based) things there's no spam. The BBs these days are totally GUI based so if you can play a video game with a chat feature then you practically don't need any training.

I heavily favour 'Trello" (see trello com inspiration business). It's just virtual decks of 3x5 index cards. SHAMELESS PLUG - For a modest retainer I can set your business up on Trello! It can make a big difference in your workflows and really reduce e-mail time wasting.