How to permanently prevent Outlook for Mac from switching to the new GUI?

every time the update automatically installs, I lose ALL of my email and ALL of my folders and saved emails that reside on my computer. My entire business will be put in jeopardy if I lose all of my previous email and email history. I must stop this update from happening automatically.

How can I stop the update or alternatively have Outlook restore my email organization EXACTLY as it had been before the update?

Same question here...

The banner atop my outlook says that the next time Outlook restarts it will launch the new outlook and like you all, I already battled with the mess of new outlook.

The "Contact Support" answer to my question of how to opt out of the new outlook said:

Currently the option to disable the prompt window is not available. We have notified the engineering team about this, and the concerned team is working on it. Since this needs to be tested and the fix needs to be rolled out, we would not be able to provide an ETA on the same.

However, if you do not wish to see the prompt anymore, kindly follow the below instructions - 1. Open Terminal (this can be searched from Spotlight located at the top right)2. Type in the commands as under -defaults write com.microsoft.Outlook EnableNewOutlook -int 03. After which, hit enter in TerminalThis should disable New Outlook and the prompts for it.

In response to my question if the terminal command will prevent the switch or just remove the announcement, the answer was:

Yes, the prompt to switch to New Outlook will not appear anymore and it will not switch to New Outlook interface automatically.

I completely agree with this assessment!

I concur with ALL of these users and replies. My wife has an IMAP account, which she prefers to a more standard server account. I have read that the New Outlook does not fully support IMAP accounts. In any case, last night something happened to inadvertently switch to the New Outlook, and ALL OF HER PAST EMAILS DISAPPEARED from her Inbox, as well as from all of the numerous subfolders she has set up. The subfolders disappeared as well. Thankfully, reverting to the old Outlook made everything reappear.

I WANT TO DISABLE THE ABILITY FOR MY MAC TO SWITCH OVER TO THE NEW OUTLOOK. No software should force a user to adopt it, or otherwise 'coerce' them to do so. PLEASE FIX THIS.

Thanks to all of the other users for sending in their replies. I'm glad to know we are not the only ones seeing this issue.

As a backup plan, I have exported my mail and copied everything across platforms. A .pst resides on a Windows environment and my main mail identity on Mac is copied to an external disk. Since I had an earlier issue with Outlook, I started using other mail apps, just to have my mail in another storage as well. I’m not really actively using those apps, but I fire those up, just to make sure I’m not jeopardizing anything. A suggested precautionary measure, that could potentially be a lifesaver. Thunderbird, Apple Mail, Spark, Canary. Pick one, or two, and at least backup your mail storage/cache.

Users shouldn’t be forced into taking these extra and cumbersome actions, but better safe than sorry.