There is a simple way to move your Apple Mail mailbox to Outlook PST. I just recently went through the same process and found it. I tried a few manual ways that were too complicated and took too much time before I found
Mailvita Apple Mail to Outlook Converter, a tool that made everything easier.
In short, this is how it performs:
To begin, save your Apple Mail info as an MBOX file.
Then, open the MBOX file in the Mailvita conversion tool.
The tool scans the data and lets you turn it into a PST file that you can then load into Outlook.
It's even possible to split big PST files while keeping the folder structure, which I found very useful.
The interface is easy to use, and I didn't find any bugs or strange formatting problems. It's also easy for people who aren't very tech-savvy to use. It only takes a few clicks to install and you're ready to go.
I hope that helps someone else! This application made it a lot easier to move from Mac to Windows or just from one email platform to another.