neowin[.]net/news/outlook-personal-email-accounts-will-do-away-with-basic-usernames-and-passwords-september-16/
theverge[.]com/2024/6/11/24175917/microsoft-outlook-security-changes-secure-future-initiative
Today web sites, PWAs, and email apps can use Basic Authentication [the old-fashioned user name and password method] or Modern Authentication to sign in and send/receive email. Starting September 16th, only Modern Authentication will work with Microsoft's email services -- outlook[.]com, hotmail etc. This *may* pose a challenge if you've been using Windows Mail for a while, as accounts may have been initially set up using the Basic method, and you might find that setting up accounts today using Modern Authentication in the Mail app can be broken.
Microsoft is also removing the ability for consumers to access Gmail accounts in Outlook.com at the end of the month. This feature was originally introduced in 2019 as a way for Microsoft to integrate Gmail, Google Drive, and Google Calendar into its Outlook.com web mail client. The new Outlook for Windows app and Outlook for Mac will still support Gmail accounts, though.
Microsoft is also planning to remove the light version of the Outlook web app on August 19th, which was originally designed as a lightweight option for older browsers.