Transferring emails from Outlook Express for Mac OS 9 to Mac OS X Mail

The data files are held in the Microsoft User Data/Identities  folder.

Copy the folder MacintoshHD/Documents/Microsoft User Data/Identities from your old OS 9 Mac into the folder /Users/UserName/Documents/Microsoft User Data on your new OS X Mac. (Any Identities folder already will be overwritten -which is OK if the computer is new and there isn't anything data)

On the new OS X Mac you can check everything has copied OK by launching Outlook Express (in Classic mode).  You can also import from there into OS X Mail (which may take 2 goes).  InBox & Sent Mail goes to Mail.  Contacts goes to Address Book.  To do this, run Outlook Express & Export Contacts.  Then open Address Book and Import from a text file using the file just exported.