At some point, Modest will replace the default email client on the ITs. For now, it's a separate application that must be launched on it's own.

Modest uses the internal Contacts list, flashes the LED, and pops up a mail notification icon on your IT's desktop (just like the default email app).

Claws does not use the internet Contacts list (although I've been trying to get the developers to add that feature forever now!). As of a pretty recent version, it does flash the LED. But, it doesn't popup any icon notifications on the desktop (and I don't know if it ever will).

As far as Contacts in Claws goes, you can import contacts (vCard format) and add your own. There's also an app called ContactInfos that allows you to integrate GPE Contacts (and other Contacts apps) with other maemo applications... I haven't had time to test it yet, though.

-T.