To successfully import a "maildir"-type of mailbox into Outlook, you first need an intermediate step.
The intermediate step involves the conversion of the "maildir" mailbox into the "mbox" format first.
Once you have the single mbox-file, you can then extract the *.eml messages (& subsequently open them with Outlook).
1) "maildir" To "mbox" conversion.
Login to your Cpanel server and locate the user's maildir mailbox.
cd into the ~/user.name/cur-folder.
Create/Launch the "mdir2mbox.sh" script on the "cur" folder:
root@www-wa-01 [~/user.name/cur]# cat mdir2mbox.sh
for file in `find ./ -type f`
cat $file | formail >> mbox
The above script will create a single “mbox”-file whithin which you will find all the original e-mails.
2) "mbox" To "eml" conversion.
Now transfer the single mbox file into a Windows PC, then Download the free tool MBOX Email Extractor and Run it.
MBOX Email Extractor is a freeware utility made by those guys: http://www.outlookimport.com
IF you Open the mbox file thru MBOX Email Extractor, you'll then be able to extract all the eml messages, ready to import into Outlook (or any other app that supports the eml format)!
You end result should be similar to as follows: