I have posted a reply to your thread in the "General" forum, where you described your actual problem.

To summarize the problem:
Your memory does not have enough free space for you to send and receive messages through the email application, although you can still access your webmail through the browser. You have cleaned out the email Inbox, and you are puzzled that the email application says there are still 567 messages.

Have you looked at the "Sent" messages and the other folders listed under "Nokia N810"?

Reflashing seems like a drastic solution to this problem, although it is a useful skill for any Maemo user.

Maybe you have already sold your N810 to peterleinchen. Pity.