How to redirect mail from a main inbox to only your smart mailbox? I have an Apple Mail smart mailbox set up to filter out all of the messages that contain a certain string in the subject line.

Now, the problem is that there are A LOT of these messages and so they clutter up my main inbox. As it stands, I can simply see the messages in the smartbox, but they reside in the main inbox. 

Is there anyway I can get these messages to move from my main inbox to the smartbox?
A smart mailbox is just a virtual mailbox showing mails which match certain rules. This means that you can't physicallye move mail into a smart mailbox.

In your case you could create a physical mailbox folder instead and use mail rules to move mail matching the subject string directly into this folder on arrival. Apple has a support article explaining how to use rules which might help here.