Apple hat dazu in der Knowledge Base in Artikel Nr.: 106778 folgendes veröffentlicht:
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I. Moving (non-AOL) email messages using IMAP
1. Open the email application program on your non-Macintosh computer. If you have not already connected this computer to the Internet, do that now.
2. If you do not already have an IMAP mail configuration in the source application, add one now. See Notes 1 and 2 at the end of this section.
3. Locate the Inbox for the IMAP account in your email application. If you were not already using IMAP, note that this is different from your previous Inbox.
4. If desired and applicable, add custom subfolders to your IMAP Inbox See Note 3.
5. Locate and select messages, or folders of messages, that you want to move to Mac OS X Mail.
6. Drag the selected messages to the IMAP Inbox or custom IMAP subfolder. The selected messages will be uploaded to your ISP's IMAP server. See Notes 4 to 8.
7. Connect your Macintosh computer to the Internet. If you cannot connect both computers at the same time, you may need to disconnect your non-Macintosh computer from the Internet.
8. At the Macintosh computer, choose Applications from the Go menu.
9. Open Mail.
10. If you do not already have an IMAP account, create one. See technical document 106683, "Mac OS X: How to Set up Mail".
11. Select the IMAP account that appears beneath Personal Mailboxes. If you do not see your Personal Mailboxes, choose Show Mailboxes from the View menu. Mail communicates with your ISP and displays messages contained on the IMAP server. Your IMAP Inbox, and any custom subfolders, appear. See Note 9.
12. Select the messages from the IMAP Inbox or subfolders, then drag them to the desired folder or mailbox in Mail. See Notes 5 and 10.
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Das ist nur ein Auszug, auch für POP-Accounts ist die Vorgehensweise beschrieben.
Eine ganze weiterer Möglichkeiten zum Transfer und Import von bestehenden Maildaten in MOX-Mail sind dann hier im "Knowledge Pool" zu finden.
Es gibt scheinbar eine breite Palette an Möglichkeiten, so das man die für sich am angnehmste auswählen kann.