Lifehacker pointed out a great article on NewsForge.com that gives tips on how to get the most out of Mozilla Thunderbird. Thunderbird is the email client I use everyday.
I've already taken the suggestion of creating a Smart Folder to filter server status messages out of my main IMAP mailbox. This saves me some time because I don't have to type the search criteria into the QuickSearch box once or twice a day. It also provides me with a handy way to delete these messages en masse after I've reviewed them.
I'm looking forward to trying out Thunderbird extensions that the author recommends. I just heard about the Contacts Sidebar for the first time today when I was researching syncing the email addresses in Thunderbird with those in my Treo via Palm Desktop.