i have been using k-9 but it doesnt seem to update correctly. ill check the email then read or delete everything, yet it still shows i have xx number of new messages....
I am pretty sure this has something to do with your deleting options.
In your settings when you delete the message on your phone, you can set it to do different things to the message on the server, I think it's setting is to do nothing, can't recall for sure.... anyways, that number, to my bestknowledge is the email count on the server, not your phone.