In Apple Mail, is there a keyboard command to shift focus from a message to the message list In my usual review of email, I have the message preview pane open and use the keyboard to delete, archive, or skip messages with the focus in the message list.  Sometimes I want to click a link in in an email.  When I'm finished with that, I usually switch back to Mail using ⌘-Tab.  In that case it takes a mouse/trackpad gesture to put the focus back in the message list.  Normally, I would expect to be able to use ⌥-Tab to shift focus between the panes, but instead, the focus moves to individual items in the toolbar and skips the message list.  What am I missing?
On macOS Mojave, tab cycles between Mailbox list, message list, message and search bar.