I've decided to stop using Modest and use Alpine instead. It's command line, of course, but actually if you enable mouse support you can click on things with your finger (or better, with the stylus).

But for me the actual benefit of alpine is that I can use the HW keyboard without any need of touching the screen

The only thing missing is a way of notifying a-la-Maemo when I new mail comes. Pine/Alpine can write to a FIFO file when a new mail arrives. So all I need is a script which reads from that FIFO and makes a notification (vibration, LED, text -- it's all just a couple of dbus-send commands).

When I do that I'll post details about it. I'll miss Nokia Messaging, but having a full-blown IMAP4-capable kick-*** e-mail client on a N900 is worth everything.

(OK, no off-line IMAP, but you can locally save your e-mails.
Alternatively, I might investigate actually using offlineimap so that both pine and modest can fetch from the same local server).