How to transfer E-Mails from one mac to another?

Question

I have multiple E-Mail accounts which I use with Apple Mail on macos, one of them is an university account which is no longer active, which means that I don't have access to the IMAP server anymore. I would like to move these E-Mails to a new and fresh installed MacBook-Air, so that I can keep browsing and searching through those old E-Mails.

I definetly would not want to restore my whole macos installation from my Timemachine backup on this new M1 mac. I just need to transfer my E-Mails from the old computer to the new one.

I would prefer to do this with my other accounts as well since downloading all the E-Mails over IMAP will take a long time on my internet connection.

Any good ideas?

Answer 1

Export on the old Mac and Import on the new.

Any mailbox (what looks like a folder in Mail's Sidebar) can be exported. The steps I would use (skip 1 and 2 if your messages are already organised):

1. Create a new mailbox in "On My Mac" by clicking on the + sign next to "On My Mac" in the sidebar.
2. Copy messages into the new mailbox.
3. Command-click on the mailbox and choose Export.
4. Choose the location for the exported mailbox.

This creates a folder containing the messages in mbox format.

When you have transferred this folder to the new Mac, use Mail's Import command to import the messages. The newly imported messages will be in "On My Mac" and you can keep them there.

Alternatively:

Import directly from the old Mac's Library into the new Mac's Mail.

This has less steps but is more prone to error or confusion. With both Macs running on the same network:

1. From the new Mac connect to the old Mac and locate the user's home directory.
2. Use Shift-Command-dot to show hidden folders.
3. Find Library/Mail.
4. Search in the subfolders for wanted mailboxes and import.

IMAP enabled mailboxes.

For your mailboxes to which you can connect with IMAP, I recommend letting Mail download all the content. Trying to short circuit this download is prone to getting duplicates.