New Outlook won't open .pst files

No, PST files allow you to horde emails... PST's were inaccessible to everyone except the archive owner, which makes it impossible to retrieve, what is typically corporate information, by anyone else.

Email of business value should be recorded in your company's information repository, most likely your SharePoint site that is pertinent to the business activity to which the email references. This way, the enterprise, or at least those with access to the SP site can utilize it as an information asset.

If they are being used for reference, then I highly suggest that you start to use one note to organize your reference material. You can even drop the pertinent email into the note page.

One Note? I've never worked out how to use One Note for anything.

YES, it is time to drop OUTLOOK like a hot potato!

ARCHIVING:

MailStore Home [Windows]

DESKTOP EMAIL CLIENT:

emClient [Windows]

ANDROID MAIL CLIENT:

FairEmail

Look "within all apps" in the start menu. You should find the old outlook app. it is like that for me

Hoarding emails is one thing that can be resolved in different ways, but if you have to conduct an email investigation using Microsoft's Compliance tool, you will get a PST file with the contents of the investigation. Once the old Outlook client is gone, there appears to be no way to open the PST file that MICROSOFT generated. THAT'S the biggest issue I have found with this apparently short-sided decision.