I've seen plenty of recommendations pointing to third party products to migrate from Thunderbird to Outlook.
Why is this functionality not built in to Outlook. I would have pushed harder here to keep Thunderbird if I had known
it was going to be such a pain (& pricey). Is MS not interested in attracting customers?
TIA
Going to speculate that the amount of "new business" wouldn't come anywhere close to what it would cost to add the capability and probably unprofitable taking support into account. Cost is a composite of initial development, testing, on-going support
and everything else that must be maintained for that activity etc - none of which is cheap. For instance, if a problem arose and it was an issue related to corrupt TBird files - why should MS suddenly take on the responsibility of having to "prove"
that the underlying data is faulty just "because" they are Microsoft and the user opted originally to use a "free" option.
Don't know what options you have looked at but one that has had consistently high rankings from anyone who has tried it (leastwise that I'm aware of) is a solution from the folks at <Fookes Software> which is considered by others to be easy, fast,
and cost effective. (When I tested it once a couple of years ago - also found it to work exactly as advertised)
Export Thunderbird to Outlook
http://www.aid4mail.com/export-thunderbird-to-outlook
Disclaimer: The above link is provided as information only and your own due diligence should be done. I have absolutely no vested interest in either the product or company in any way.