Outlook was redirected to the server autodiscover-s.outlook.com to get new settings for your account
The URL displayed is https://autodiscover-s.outlook.com/autodiscover/autodiscover.xml. You should click on Allow only if you trust the source of your exchange, or the administrator instructs you to do so. You can check the box and click on Allow or deny. If you don’t check the box, you will be prompted every time you launch Outlook.
How to suppress the AutoDiscover Redirect warning in Outlook for Mac
When Microsoft Outlook 2016 for Mac connects to an Office 365 account, Autodiscover is redirected from HTTP to HTTPS. This is where you receive the warning message. If you choose to allow and trust the source, you will not be prompted again.
Disable or Enable Auto Discover for Outlook in Mac with Office 365
Assuming you do not want, and your administrator also suggest not to do that, then here how you can disable auto-discover prompt for Outlook on Mac. Follow the steps:
Quit Outlook if it’s running.Press Command + Spacebar, and type Terminal.When it appears in the search, select it using the down arrow, and open it.Enter the following command in the Terminal window, and then press Enter.
Close terminal.
If you want to disable, then use false instead. The TrustO365AutodiscoverRedirect preference can be configured to use the following values: Post this, you will not receive any message about allowing and trusting the URL source for your Outlook on Mac. I hope this bit helps!
