The side-by-side view has been available for Outlook Classic since May 2023 and Teams Chat since December 2023.
With the side-by-side view Edge for Business opens an email or Teams Chat next to the web page. This should prevent the focus from being lost.
The new Outlook for Windows will also support the side-by-side view until the end of October. If an organization has implemented global configurations for Outlook Classic and Teams Chat, the new Outlook will use these configurations too.
Like Outlook Classic, the new Outlook also uses the settings from the Edge browser sidebar.
If a link from an email is opened via Edge for Business, Outlook opens the email side-by-side in Outlook on the web. This means that Outlook’s focus is not lost. The email opens in read mode. It is currently not supported to reply to the email in the side-by-side view.
Microsoft describes in the documentation how administrators can customize the side-by-side view.
Update from 5 October 2024:
The rollout should be completed by the end of October.
