Q: Backing up MIT mail in Apple Mail

Please note that once you have followed the steps below, any messages that are under the "On my Mac" folders may not be seen on another device as they are now stored locally on the computer. Due to this, IS&T strongly encourages you have a backup of the computer using the Time Machine software built into the macOS. Steps on how to configure Time Machine can be found at the following Apple Support Article. (NOTE: Time Machine requires the use of an external hard drive)

Answer

You can either manually drag messages from Mail's message list to your computer (to your desktop, for example) to create copies, or follow these steps to create a local archive folder in Apple Mail:

Create an offline mailbox on your Mac

If you have not yet created a local "On My Mac" mailbox to save MIT messages to, follow these steps. If you already have done this, skip to the next section.

1. Open Mail.
2. From the Mailbox menu, choose New Mailbox....
3. In the New Mailbox sheet, choose On My Mac from the Location pop-up menu.
4. Enter a name in the Name field such as "Copies of MIT emails." or "Local backup".
5. Click OK.

You'll notice that the new mailbox appears in the list of Mail mailboxes with a large or small folder icon.?
Copy/back up messages to your offline mailbox

Move your folders and messages to local (On my Mac) folders

1. Open Mail.
2. Select the message(s) in your MIT mailbox that you want to copy/back up.
3. From the Message menu, choose Copy To > (Name of your offline mailbox).
   Alternatively: you can Control-click or right-click the message(s) and choose Copy To > (Name) from the contextual menu; or you can could hold Option while dragging the message (without opening it) to the mailbox folder icon in Mail.

Use Copy To, not Move To when creating a copy. The Move To menu choice copies messages but also removes them from their original location.

Your copied mail will now be available on your Mac even if you are offline. To access copied messages, click the offline mailbox's folder icon.