In a world where humans play an exception handling role, email has become the primary means that business processes (sometimes in the form of our co-workers) use to get our attention. Build all the fancy workflow systems you want--email will still carry most of the workflow messages in your organization. That's one of the reasons that ways to fight SPAM have become so important: they keep the work flowing and uncontaminated.
The SNARF (Social Network And Relationship Finder) project at Microsoft asks "why doesn't the email client do more to sort mail intelligently?" SNARF, which can be added onto Outlook now, performs email triage using information about who you've emailed and when. From the SNARF site: "SNARF was built around the notion that social network information that is already available to the computer system can be usefully reflected to the user: a message from a manager might be seen differently than a message from a stranger, for example."
My email client, and yours, I suspect, give you very limited options in how you sort your mail. Like your mail most-recent-first? Then you're in luck. Want it sorted by something more complex such as importance of the sender to you based on past activity? That's a harder task, albeit not impossible. Most email clients have that information available to them--they just don't use it.
In an interview with c|net, Marc Smith, one of the Microsoft researchers who developed SNARF, said "If my dog can tell who strangers are, apart from friends...my e-mail reader should be able to do the same." If only email smelled...no, on second thought, scratch that.