Hawk Wings has tracked down
on a tantalizing v2.0 update to Thunderbird, Mozilla's email client. New features at the top of my list are message tagging, a tabbed message viewer and a built-in notification system. It's great to see more developers bringing the tagging paradigm to email, as Scott Morrison has done with his MailTags
plug-in for Apple's Mail.
Check out Mozilla's Thunderbird development blog
for the full (and lengthy) post of what's coming in this major release for Thunderbird, including plenty of Mac-specific features and fixes.