We were running on a demo key.
When I replaced with a permanent no handhelds can do lookups or send email from the handheld.
If I do a wireless activation (all at version 4.0), the handheld can send email and do lookups.
However, for the 7280's at least, the enterprise activation icon on the desktop remains.
In the progress screen it says -
is now enabled
and goes no further.