Ernie the Attorney has an interesting blog post on managing email. His professed greatest tip is that not all emails require a response. Read the post for the explanation as to how he determines whether or not an email requires a response.
I also have a tip. If you're like the typical librarian, you subscribe to multiple listservs and get a number of listserv related emails every day. What I've done is to create Outlook folders for each listserv and to create rules to shuttle emails from the listservs into their proper folders. This means I don't have to read all the emails immediately, I can check them regularly. I do, of course, read the ones from the DALL listserv almost immediately.
Does anyone else have any great tips for managing email?