I use the IMAP interface to Gmail. It keeps everything synchronized between my phone, Evolution (Linux mail client), and the N800. As I read mail, I archive it, by putting it in a folder created by default by Google named "all mail." This works surprisingly well, as new mail is pushed to devices, but the archived mail is only downloaded if you open the "all mail" folder and open it manually.

And the inbox on the web interface works exactly the same way. Overall I think it is about the best email solution I've used, even better than Outlook.