Microsoft, or rather the relevant product teams, have today made a number of announcements regarding the Deprecation of various services.
Here is a summary of the announcements.

The three most important points announced are as follows:


Abolition of Basic Auth for

Basic authentication is a common method that applications use to connect to servers, services, and API endpoints. It involves sending a username and password with every request, and storing or saving those credentials on the device. Most servers or services enable Basic authentication by default, and it is easy to set up. 

However, Basic authentication has some drawbacks. It makes it easier for attackers to capture user credentials, especially if the credentials are not protected by TLS (Transport Layer Security). This increases the risk of those stolen credentials being reused against other endpoints or services. Moreover, Basic authentication does not support or facilitate multifactor authentication (MFA), which is an additional layer of security for user accounts. 

After removing Basic Auth for Exchange online in commercial Microsoft 365 Tenants, Microsoft will now force Modern Auth/OAuth 2.0 for as well. That means that all clients connecting to must definitely use the new methods. 


Reminder that Mail/Calendar will no longer be supported by end of calendar year

Microsoft has announced that the Mail and Calendar Apps will be phased out by the end of 2024, transitioning users to the New Outlook for Windows.

Users are currently able to test the New Outlook while retaining the option to switch between it and the Mail App versions. Supported Accounts include Microsoft 365 consumer accounts like,, and, as well as Microsoft 365 work or school accounts and Gmail. Plans are underway to extend support to Yahoo!, iCloud, and other email providers through IMAP and POP in the future.


Microsoft Message Center Details In Part

MC590123 · Published Jun 2023. Revised to include new information August 30, 2023

We will replace the Mail and Calendar apps in Windows with the new Outlook for Windows by the end of 2024.

After this change is implemented:

  1. Users can no longer use or download the Mail and Calendar apps.
  2. Users with a Microsoft 365 or Office 365 subscription with access to the Microsoft 365 desktop apps can use the new Outlook for Windows.
  3. Users can use the new Outlook for Windows with any personal email account (, Gmail, etc.), even without a subscription. 
    • If you would like to prevent users from adding their corporate email accounts to the new Outlook, you can follow the instructions in this document to disable the application for a single user, group of users, or the whole tenant: 
    • In mid-September 2023, we will begin auto-migrating Mail & Calendar app users to the new Outlook for Windows with an option to go back if they choose. Users can return to the current Mail & Calendar apps by clicking the toggle in the new Outlook for Windows. We also want to reiterate that these changes will not affect your organization’s use of classic Outlook for Windows. 


Minimum browser version for accessing

One of the ways to ensure optimal security and functionality for the web browser is to keep it updated to the latest version. Most modern browsers have the feature of updating automatically, such as the new Microsoft Edge, but the user should check if the auto-updates option is enabled in the browser settings. For Microsoft Edge and Internet Explorer, the updates are delivered through Windows Update, which is another feature that the user should activate and install the updates as soon as they are available. 

OS Version Browser
any Microsoft 365 for the web The browser in which Microsoft 365 is opened.
macOS any Safari (version 16 or newer)
iOS any Safari (version 16 or newer)
Android any Chrome
Windows 10 Non-subscription Office 2013 or later Internet Explorer 11
Windows 10 ver. < 1903 Microsoft 365 Internet Explorer 11
Windows 10 ver. <1903 Microsoft 365 ver. < 16.0.11629 Internet Explorer 11
Windows 10 ver. >=1903 Microsoft 365 ver. >= 16.0.11629 AND <16.0.13530.20424 Microsoft Edge
Windows 10 ver. >=1903 Microsoft 365 ver. >=16.0.13530.20424 Microsoft Edge *

* Requires Microsoft Edge WebView2


Retirement of OWA Lite

Also OWA Lite will be retired – This was the experience that unsupported browsers had that provided a very basic experience.

The image below shows the light version of Outlook:


This means an old browser that’s incompatible with the new and Outlook on the web is in use.


As we can see, this light version still looks like OWA light from Exchange 2010 just with a replaced OWA logo.

Screenshot from Exchange 2010 SP3 OWA light:

We think this is the last remainder of the /OWA virtual directory in because all current versions of Outlook are running in /mail.

You can still access this version using the URL:

But not for long anymore because this light version will be retired now.


In the following link, you can find the original article from Microsoft:



Drago Petrovic

Microsoft professional for Microsoft 365, Data classification, Microsoft Exchange, Teams Voice, PowerShell and Cloud services. Working as Principal System Engineer and Cloud Solution Architect in a Swiss IT company. Also, a Trainer for Microsoft Cloud services and Web 2.0 in Swiss schools.

5 times Microsoft MVP

Rolf Tröndle

Microsoft Certified Master & Solutions Master (MCM/MCSM) in Exchange 2007, 2010 & 2013

Microsoft professional for Microsoft 365, Exchange Online, Teams.
Working in my own companies in Switzerland for customers ranging from 5 to 100'000 seats.
Also, a teacher for Data Compliance & Data Privacy at a University for applied sciences.

Microsoft MVP