This function passes control through to the relevant section. It serves as the main entry point for the Mail Queue stuff.

• Redirects to the appropriate function based on the sub-action
• Requires the admin_forum permission
• Uses the standard "show_settings" sub-template
• Defaults to a sub-action of 'browse' if it isn't specified or isn't valid
• Accessed at .../index.php?action=admin;area=mailqueue[;sa=sub-action]