How to best move / import my previously received email from Outlook Express into Mail.app? This is a question often asked by switchers (Windows PC -> Mac)
On the Windows

Download Eudora for Windows and install it if it's not already on your computer. Eudora can be used for free in sponsored or light mode.

If you see the New Account Wizard when you open Eudora, click Cancel. Go to the File menu and choose Import. It should automatically detect any Outlook or Outlook Express accounts.


Check the box next to the account(s) you wish to import.
If present, check the boxes next to Import Mail and Import Address Book Entries.
Click OK.




Your Outlook or Outlook Express mailboxes should now appear in Eudora's mailbox list. Close Eudora. If prompted to save changes to the Address Book, click Yes.

Locate the newly created Eudora mailboxes and address book so they can be transferred to the Macintosh.


Use the Search or Find option in the Start menu to locate "Outlook Express.fol" or "Microsoft Outlook.fol" (depending on which program you are importing from). You may need select Search hidden files and folders under More advanced options.
Right-click the .fol folder in the search results and choose Open Containing Folder.
Transfer the .fol folder and the folders called "attach", "Embedded", and "Nickname" (all in the same location) to the Mac (e.g., via recordable CD, USB flash memory drive).


On the Mac

Download Eudora Mailbox Cleaner.


To properly import all messages, attachments, and address book entries, the files copied from the Windows computer must be arranged in a specific manner.
Create a new folder and call it "Eudora Folder". The Desktop is a good place to create the folder.
Inside this folder, create three more folders named "Mail Folder", "Attachments Folder", and "Parts Folder".
Move the "Microsoft Outlook.fol" or "Outlook Express.fol" folder into the "Mail Folder".
Move the contents of the "attach" folder into "Attachments Folder".
Move the contents of the "Embedded" folder into "Parts Folder".
Move the "Nickname" folder into "Eudora Folder".
Make sure Mail.app is not running, then drag the "Eudora Folder" and drop it on the Eudora Mailbox Cleaner icon.
Leave all the boxes checked and click OK. (Filters will not be imported because Eudora cannot import the original filters from Outlook or Outlook Express.)




Eudora Mailbox Cleaner will display the results of the import. If the import was successful, the number of imported messages, recovered attachments, and imported nicknames should all be greater than zero.



Your messages should now appear in Mail.app in a folder called Import. Address book entries should appear in the OS X Address Book application.

NOTE: If you are unable to open the imported files, you may need to rebuild them. Select each folder, then go to Mailbox > Rebuild.