Welcome Don!
Are your old emails in Outllook or sometihng else? Both Outlook and Apple Mail have Export and Import options that are how I've alwasy moved mail.
Import or export mailboxes in Mail on Mac - Apple Support
At least on the Mac side, dragging did not work for me but importing did.
As MS Office/Outllook is not an Apple product and there are not as many Office users active here as one would think, I believe you should also ask in Microsoft's Office forums. MS Office questions posted in Apple’s forums tend to linger a long time before getting any kind of helpful response.
The only trick is limiting views to Mac issues, and that’s easy.
Start here:
Results in Office - Microsoft Community.
That will display this page header:

1) If needed, use the “Office Topic” pull-down to select your Office app.
2) Limit answers to Mac topics with the “Office Sub-topic” pull-down.
3) If needed, use the “Show Filters” option to further narrow the results.
Everyone there is both an Office user and a Mac user, something you can't say about Apple's forums. I believe you will find the contributors there knowledgeable and very helpful.