It’s no secret that I love Mail’s Smart Mailboxes feature and rely on it to keep my messages sorted and under control. One sharp-eyed Quick Tip reader caught that I keep my Smart Mailboxes grouped and and asked how I did that. The answer is easy — once you know where to look.
To make a folder in Mail that can hold Smart Mailboxes, choose Mailboxes > New Smart Mailbox Folder. Give your Smart Mailbox Folder a name, and click OK. 
Creating a Smart Mailbox Folder
Drag Smart Mailboxes into your new folder to organize them, and like other mailbox folders, you can nest your Smart Mailbox Folders if you like.
I group my Smart Mailboxes into folders so that I can more easily find similar messages based on the searches each folder performs. For example, I have a set of Smart Mailboxes that search for messages based on how old they are relative to today. I have other sets that group messages based on senders, and notes I’ve added to messages with MailTags. 
Group Smart Mailboxes with Smart Mailbox Folders
I like Smart Mailboxes because they organize messages without actually moving the emails they find. Smart Mailbox Folders let me add an extra layer of organization to my constant stream of emails and make all of that incoming content more manageable.