Version:           1.9.3 (using KDE KDE 3.5.3)
Installed from:    SuSE RPMs

Navigation keyboard shortcuts (as appropriate, but at the very least 
"_n_ext" and" _p_rev") should work in the standalone message viewer.

This is related to:

Separate reader window should have "Previous- / Next Email" Buttons
http://bugs.kde.org/show_bug.cgi?id=71963

but is distinguished by being a wish for existing bindings to work in 
the standalone context, rather than for new buttons. This is explicitly
_not_ a request for additional buttons, and should not be merged with
that wish.

I think this is consistent with Kmail's "focusless" approach to key 
bindings that I've seen discussed here.