You don't need to use all the mailboxes that you have all the time. You can view them as 'tabs' and tabs are sticky. Once you open the folder or a mailbox as a tab, they will remain there until you close them. So you can customize your view via tabs.
You can add folders, mail activities, sent folders, etc as a tab.
Below is how to add a folder as a tab:
and an inbox, mail activity, etc as a tab:
