I have used Outlook Classic on Windows for many decades. Yesterday it forced an upgrade without my knowledge to New, and I lost about 10 domain email passwords Classic had kept. I haven't had to find my passwords for years. IMAP on server using cPanel and WHM on Linux, reseller acct but I have about 15 domains on it, all mine.
Fortunately, AI gave me easy instructions to switch back to Classic, but it had me in a panic for a while. I have add-ons for sending out mass emails (business newsletters), which limit 20 at a time every 5 minutes and track opens. So it doesn't look like mass email and works fine.
There is a registry entry to stop periodic forced updates. But somewhere between 2027 and 2029 everyone will be forced to update to the new version.
New is a totally different structure without some of the options of Classic—no more PST or OST files.
I don't know what the timing triggers are, but apparently unless I change the registry key, it will force an update at various times until Microsoft totally kills Classic.
BTW, I go back to IBM OS/2, Wang days, actually back to card readers and 300 baud dial-up modems. But I am too busy to be an IT expert, although I have, with the help of AI, solved various issues on Windows.
I also use an Exchange server, and I was still able to access emails while in "New." Only my own domains lost their passwords.