I feel like I need to point out that I haven't deleted a single email in my gmail so there's stuff in there going back to 2006 or... I dunno whenever gmail first hit the internet.

Everything is "read", though. A lot of times I just skim the subject and if it's not important I'll mark it as read without actually opening it.

I use Thunderbird because I want to have Mozilla's babies and it helps me keep track of my emails as they come in