There are plenty of posts about emails overload at work, email organization, email productivity… There are even interesting blogs dedicated to the subject.
Actually, increasing email volume is a reality we have to face up. Here is how I try to deal with the «Inbox overload».
* Folders: I automatically organize inbound mail into folders: as I belongs to different email lists, I like to get inbound emails automatically classified based on the destinatory lists to which I belongs; I have a folder for each list.
* Thread (pre)view: I organize emails in each folders by «Conversations topics» (Outlook), filtering «unread email» only, and I enable the «2 lines Autopreview»: I get a fast preview of full conversations with unread (new) mail. That way, I can see rapidly the topic of each thread and if it has already been dealt with by any list member (generally a colleague). I’m able to fastly discard full conversations (possibly tens of email) in a minute — «mark as read» button is your friend!
* Snarf: I sometimes also use SNARF, the Social Network and Relationship Finder, from Microsoft Research: It let me see if I have new unread emails from people which I frequently exchange with. I can also fastly mark those emails as read and or delete them.