Just a while ago, I got a request to migrate emails from a Windows XP machine running Outlook Express. I am glad my client decided to make the upgrade to a new PC running Windows 10 to improve security.
If you are looking for a way to migrate emails from Outlook Express into Thunderbird or Outlook, here are your options.
As you can see, unless you are willing to pay for a third party software to convert the files, you probably will not be able to import the emails into Outlook for free.
Well, there is another method and it is 'free' as discussed below. Although you need not pay for any software tool, there is still time and effort involved in carrying out the process so somebody has to 'pay' for that I suppose.The concept is simple. Copy the emails manually to the mail server via a temporary IMAP account. Once done, synchronise the emails to the new mail client. The main considerations are:
Whichever method you decide to use, always backup data into an external drive as a precaution against Murphy.