Outlook App opening a browser Tab

As of build Microsoft® Outlook® for Microsoft 365 MSO (Version 2211 Build 16.0.15831.20098) 64-bit this issue no longer affects the calendar selection... Now every time we open the outlook desktop app, it launches the web version. This is happening immediately the Outlook Desktop app is opened.

Out of 15 users, I have one experiencing the browser opening when she starts her Outlook Desktop app (we never experienced the calendar issue). It's very consistent in that she can open/close Outlook and it happens every time. It's like a behind-the-scenes login process that's being displayed with no login prompts, just the animated mail icon you might see after successfully loggin in. She's been getting it for many weeks now. We're on the same version (Version 2211 Build 16.0.15831.20098). I've attached the browser URL that's displays at that time. The obfuscation is her login account.

We are having the same issue, although with some additions. We get users having a browser popup with error 500 when creating new meetings and users having error 400 popup in a browser when they open outlook or try to edit some messages.

I was able to take care of some of the ones related to the meetings with the following regedit in a gpo

Key Path: HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\Options\Calendar
Key: ShowLegacyRoomFinder

Type: REG_DWORD

Value: 1

I have noticed that the other errors are occurring on this web page:

https://login.microsoftonline.com/common/oauth2/authorize?client_id=00000002-0000-0ff1-ce00-000000000000&redirect_uri=https%3a%2f%2foutlook.office365.com%2fowa%2f&resource=00000002-0000-0ff1-ce00-000000000000&response_mode=form_post&response_type=code+id_token&scope=openid&msafed=1&msaredir=1&client-request-id=f322cfb1-88cf-79b5-3f43-09e2b277fd8b&protectedtoken=true&claims=%7b%22id_token%22%3a%7b%22xms_cc%22%3a%7b%22values%22%3a%5b%22CP1%22%5d%7d%7d%7d&nonce=638059384817229913.d8a9da8a-7062-4905-ab94-7f8c74284040&state=DctBEoIwDEbhVu7hDWpDG0iycDjLr6iwgHYGZri-XXxv97xzrmtujacWJ2NWGiwray8pmfX5MStshiIIjSmw0RDwMg7y1bdwUiYm3957LBfiVHEuz1jquZb9iBt2_D6o9fgD&sso_reload=true

I can access this webpage fine on my computer, and mine does not get the popup when I open outlook or when I mess with messages like some users do. Like others have said here I have noticed this occurring ever since recent updates.

I also noticed the error occurs if I go to File and then click on the button that says "Manage Add-ins" : "Manage and Acquire Web Add-ins for Outlook".

I have already tried repairing, reinstalling, running outlook with no add-ins enabled, creating a new outlook profile,, flushing dns, clearing browser cache, verifying network settings are correct for the users having the issues.

Email and calendar works, so I am not sure why these browser popups are necessary, especially when opening outlook.

Hope this info helps to find a resolution

Hey Paul, please keep us posted on what Microsoft tells you in your ticket with them! Currently the only workaround that I have found that still seems to be working is enabling OWA on the affected users mailbox, but this is not a great workaround when ideally we want to keep OWA blocked. Hoping MS is able to provide a better resolution than this.

We had one user experiencing this issue and now there are several with no direct idea as to how or why it is happening.

We use hosted exchange with office 365 (outlook) for access to email. We do not have access to webmail (it's blocked).

Non-hybrid for email.

Hello KAITLYN BRADLEY,

Good day!

Thank you for posting to Microsoft Community. We are happy to help you.

Before we proceed, I would require more information to assist you better.

1. What is the type of account? Is it a POP, IMAP, Exchange ActiveSync or Exchange account?

2. Please may i know your outlook version? What version of Outlook do I have? (microsoft.com)

3.Please may i know if your environment is hybrid? You can either as your IT department or if you know your Global Admin (Am asking that because if the Office is installed on a server and everyone in the company connects to that server, that kind issue can happen.)

4.Please use your outlook on the web to create new event in Calendar to see if you didn't notice any error

The problem seems specific to the 'invite attendees' function Am i right?

Please the information above is very important to find out the cause of your issue and provide you the right troubleshooting

Please get back to us with necessary information, we’ll be glad to assist you further.

Appreciate your patience and understanding and thank you for your time and cooperation.

Sincerely,

Eben Ezer Tres | Microsoft Community Moderator