We have successfully exported the email folders from his Outlook express into .dbx files. We successfully converted the files using 'DbxConv' for PC, as well as 'Email Converter Pro' for Mac. However, when we tried to import these .mbox files through Outlook (Mac) the files weren't recognised (using either of the converter programs). 

We are unsure of how to proceed, but would love to find an answer asap, as the Mac has been bought for business purposes and the thousands of saved emails are vital!

The option of importing individual .eml files is not possible as there are thousands to go through and would be massively time consuming.

Any help with this would be greatly appreciated. 

Many thanks in advance.