How do I archive my emails in Mac Mail, and free up server space?

Here is how to archive in apple mail:

Start Apple Mail
From the Mail menu select Mailbox > New Mailbox…, The “New Mailbox” window should now appear
For Location select “On My Mac”
For Name enter any name for your new local mailbox
Click OK and Your new mailbox should appear in the mailbox listing
Open the mailbox on the server that contains the message or messages you’d like to move
Select the messages you wish to move
ctrl-click on the highlighted messages to see a menu of options and select “Move To”
Then choose the folder you created previously from the pop-up menu

Result: The messages you selected are moved to the folder on your local machine. If you have a lot of messages this could take a long time to complete. Do not power off the machine, allow the battery to die, or disconnect it from the internet until this is complete.
By selecting “Move To” the messages will disappear from the mail server and will no longer count against your email quota.
Repeat the steps as needed to move mail from multiple mailboxes on the server to your preferred set of mailboxes on your local machine.

There's an Apple discussion on this here: https://discussions.apple.com/thread/3841507

If you'd prefer to have an IT person assist with this, (which we recommend) just email support@brownrice.com and we will refer you to people who can help!