(1) On your Windows machine import your email to Outlook Express.
(2) Find the Outlook Express folder containing your mail folders, which are contained in *.dbx files. By default that folder is located in the following general location.
"C:\Documents and Settings\*USERNAME*\Local Settings\Application Data\Identities\{9ECC51D4-YOUR-OWN-IDENT-BLAH-BEDED493AB3F}\Microsoft \Outlook Express"
(3) Put dbxConv into the same folder as your .dbx files
you must run DbxConv from the commandline. to get to the commandline you
(4) Go to your "Start Menu" then "Run", type in "cmd" (no quotes), navigate to your Outlook Express folder containing the *.dbx files.
(5) type "DbxConv.exe *.dbx"
then, it very quickly converts the *.dbx files to *.mbx files.
(6) After conversion is complete, type "rename *.mbx *.mbox" (no quotes)
(7) Boot into OS X, open Mail.app, go to "File" then "Import Mailboxes", Import Mailboxes from "Other", "Continue", and navigate to the Outlook Express folder containing the *.mbox files.
Mail.app will ignore the *.dbx files, and import the *.mbox files with no trouble.
(to those that will read the documentation of DbConv.exe... "-mbxextmbox" failed to convert *.dbx files directly to *.mbox.)
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i found this information at
http://jthurber.com/blog/index.php?p=119 and adapted the directions for the typical OS X / Windows dual boot scenario.
DbxConv.exe is found at
http://people.freenet.de/ukrebs/dbxconv.html