I’m currently using Outlook with a POP3 account but I’d like to switch over to an Outlook.com account.

I’ve set Outlook.com to download all the new mail for my old POP3 account (actually, I’ve set my old account to forward to Outlook.com as this appears to be faster) and configured my Outlook.com account in Outlook. This all works great and as expected.

How do I migrate all the mails which I had already downloaded via POP3 into an Outlook pst-file to my Outlook.com mailbox?