How do I prevent Outlook 365 on the Mac from launching the New Version

I would just like to add my voice to the swell of protest at this very invasive "time bomb" . My experience with the new Outlook has been time wasting, harrowing and not a positive one. Almost changed over clients as I has to reinstate a host of email accounts manually. Precious time wasted by an upgrade that failed to deliver-BIG TIME. Now to tell me that you will regularly make my decision for me and rob me of choice- that is not a good look Microsoft. This is especially so as your upgrade is a deeply flawed product. Release a version of Outlook that works, doesn't chew emails, doesn't mess up settings-then I might upgrade.

Thanks to RandallPacker for proving the terminal fix. Shouldn't have been necessary.

I would just like to add my voice to the swell of protest at this very invasive "time bomb" . My experience with the new Outlook has been time wasting, harrowing and not a positive one. Almost changed over clients as I has to reinstate a host of email accounts manually. Precious time wasted by an upgrade that failed to deliver-BIG TIME. Now to tell me that you will regularly make my decision for me and rob me of choice- that is not a good look Microsoft. This is especially so as your upgrade is a deeply flawed product. Release a version of Outlook that works, doesn't chew emails, doesn't mess up settings-then I might upgrade.

Thanks to RandallPacker for proving the terminal fix. Shouldn't have been necessary.

I soooooo agree. but typical for MS. Let the costumer do the testing. Is cheaper. And yes thanks RandallPacker, I got it to work in the end.

Has anyone else had the following problem?

I have 2 identical Mac Studios running the same macOS and Office for Mac. I entered, successfully, the Terminal command that was posted here. One of the Mac Studios two days ago when Outlook started popped up with that message the '... next time Outlook starts the new version will be started ...'. I then re-entered the Terminal command again on this computer. Luckily this worked again and this computer is still running the old Outlook. Do I have to constantly enter this Terminal command periodically? Is there something MS is doing that overwrites this command?

I have 2 identical MBP M1 and this has not happened to me. I got errors at first when I tried to use the command. Next I prefixed it with sudo and I have never had the annoying message appear again.

In case you are not faniliar with sudo, here a litle explanation: https://support.apple.com/en-gb/guide/terminal/apd5b0b6259-a7d4-4435-947d-0dff528912ba/mac#:~:text=To%20run%20commands%20with%20superuser,password%20of%20the%20current%20user.

Yes. It worked!!!