I've been using Microsoft Exchange since what can effectively be described as "The Dawn of Time". Specifically, since 1996 when we were using Exchange 4.0 and this nifty new tool called "ActiveSync". The transport was simple, the database was huge, clunky, fragile, error prone, and terribly difficult to repair - but it was the best thing available and had some great functionalities - including Public Folders - which allowed for 'company wide' sharing of information.
It was clear that there was still some development needed, because one glaring gap was that ActiveSync could not deal with Public Folder data - and everyone in the industry recognized this as a flaw, but we also trusted the Microsoft would fix it in the next version or through a patch.
The biggest problem with the inability to link ActiveSync with Public folders was that it prevented companies from effectively sharing a corporate contact list. Every person could go in at their desktops and find an address in their company's Shared Contacts in the Public Folders - which was valuable if you are sitting at your desk, but didn't help you anywhere else (for me, the frustration was on my "Palm Pilot" - but the 'PDA Boom' was just starting out and soon there would be thousands of devices). So, you copied the entire contents of the Company Contact List into your personal Contacts in Outlook, then you could sync - and you were perfectly synchronized... that minute. As soon as anything changed in the Public contacts, of course, you were out of date and would remain so until you emptied out your company contacts and copied everything over from the public folders again.
Fast Forward 25 years... and the same problem exists in the same way today. Today, we send and receive mail from our mobile phones at a rate of billions of messages per day. We synchronize every kind of data under the sun. We browse the internet on our phone, while we are driving, merely by speaking at our phone without ever taking our hands off the steering wheel! Microsoft has online services to do EVERYTHING including processing and parsing data automatically from one database to another triggered by anyone anywhere making an entry in that database, or just on a scheduled basis. We can take tests, hold meetings FACE TO FACE whether on our computer or on our phone, or tablet, or, depending on your model, you can probably do it on your refrigerator or cloud controlled home thermostat. "Honey, what are you doing in the hallway?"... "Oh, nothing dear, just having a quick Teams chat with my poker buddies...".
What can't we do using Microsoft Technology? - I mean... Its pretty amazing, isn't it?
Oh,... I know what we can't do....
WE CAN'T SHARE A CONTACT LIST INSIDE OUR COMPANY AND KEEP EVERYONE UP TO DATE WITH CHANGES AND STILL ACCESS THE INFORMATION WHILE WE'RE NOT SITTING AT OUR DESKS!
What is it about this basic problem that is so challenging to Microsoft that, even though at least one person every day over those 25 years has been asking for it, they are either unwilling or incapable of finding a solution?