[MlMt] probably foolish question

[Barton Lipman]

This is probably a foolish question but I'll ask anyway:  I use the 
keyboard for almost all navigation, but cannot figure out what 
determines whether I'm "in" the mailbox list or the message list.  I'll 
hit my shortcut to go to a particular mailbox and sometimes can hit the 
arrow key to move within the message list, but sometimes that will 
switch me to the next mailbox instead.  I know that I can use Command 
with the arrow keys to move within the message list, but would prefer to 
be "in" the message list already so that I don't need the Command key.

Is there a simple way to move from the mailbox list to the message list 
without using the mouse?

Thanks.