Even with Office running quite well on Leopard through VMware Fusion most of you switchers will still not want to depend on the messaging solution from Microsoft on your Cupertino OS. But how would the required migration work for all the emails from the past? There is no export feature in Outlook that would create anything meaningful to Apple Mail. Obviously for pure IMAP (or Zimbra connector) users as I am, it is no issue, as you just point your new client towards the right ports of your server and off you go. But I’m also an offline user as a POP3 user would be when it comes to mail archives. My thousands of received but also sent messages are nicely archived in separate local folders in Outlook format for each of the past years.
The answer to the Outlook to Mail migration question is: Thunderbird.
Simply install Thunderbird on your Windows environment next to Outlook and agree to all import from Outlook suggestions you will get during setup. Thunderbird will store online as well as offline content in the local application data folder in your home directory.
C:\Documents and Settings\[USER]\Application Data\Thunderbird\Profiles\[PROFILE]\Mail\..
The .msf and the corresponding files that do not have an ending are what you need to move over to your Mac. Mail.app has an “Import Mailboxes…” feature that you can use to include them into your local mail.app setup.
During my own migration I realized that not all files (each representing one folder from Outlook) were offered for import. This seems to be file size related. The solution here is to split them into items below 1 GB in Thunderbird before moving them over to the Mac. Note, if you split e.g. a 1.2GB file into two 600MB files you have to compact them before moving, otherwise the file size doesn’t change.
This way I successfully migrated 18’972 emails from Microsoft Outlook on Windows to Apple Mail on OS X Leopard. All available at the tip of my finger through spotlight of course.