One more useful tip for Sylpheed users:
You can switch from Sylpheed non-hildonized windows like message editor or single message view (they don't have icons on taskbar) to other window, and be able to switch back.

To do so, you must modify your current theme to add task switching functionality as described in the maemo.org Howto named "using virtual keyboard with X forwarding"

Open /usr/share/themes/_your_current_theme_/matchbox/theme.xml
I'm using LCARS so for me it's /usr/share/themes/LCARS/matchbox/theme.xml
Find first entry of word "custom". It should be button definition
Add string
<button x="320" y="0" w="60" h="60" action="next" options="inputonly,pressonly"/>
before it.
Run
# matchbox-remote -t _your_current_theme_
It will reload theme.
Now you should be able to switch between windows pressing area between status icons and window title just like alt-tab do in MsWindows.
Warning: you can't switch to minimised windows.
Have fun