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 firstname.lastname@example.org and we will refer you to people who can help!