❓ Outlook Add-In (new): Transition and architecture of the Web Add-In

This article provides an overview of the transition to the new Outlook for Windows, explains the differences between COM and Web Add-Ins, and summarizes the benefits of the new FTAPI Outlook Add-In.

The classic and the new Outlook

The classic Outlook for Windows will remain available as part of Office. However, it is intended to be replaced by the new Outlook in the future. In some cases, users can already activate and test the new Outlook for Windows.

Furthermore, Microsoft is pursuing the following migration strategy for the new Outlook:

For Microsoft 365 Business users, the automatic switch has been taking place since January 2025 (FTAPI provided information on this in December 2024).
For Enterprise customers, the transition is planned from April 2026.
The old Windows Mail and Calendar client has been discontinued since the end of 2024.

The automatic switch can be actively prevented by administrators.
Attached is a Microsoft guide on disabling the automatic switch for your users.

Outlook extensions: COM and Web Add-Ins

COM Add-Ins (Component Object Model) have been an integral part of Microsoft Outlook for years. They allow developers to integrate custom functions deeply into Outlook.

In the new Outlook, integrations and add-ins based on COM technology can no longer be used.

All integrations and add-ins for the new Outlook are based on web technology – they are therefore also referred to as Web Add-Ins.

FTAPI Add-In for the classic Outlook and the new Outlook

FTAPI provides an add-in for the classic Outlook (COM technology) as well as an add-in for the new Outlook (web technology). Depending on the Outlook version used, you and your users should select the appropriate FTAPI Add-In.

Benefits of the new FTAPI Outlook Add-In

Simplified administration

The administration of the new Outlook Add-In is performed server-side in the administration area. This makes it even easier to configure, oversee, and roll out settings for the Outlook Add-In.

In the previous FTAPI Outlook Add-In, the majority of settings were configured client-side.

Automatic updates

Updates for the new Outlook Add-In can be applied automatically. This significantly reduces the administrative effort, as users are always automatically up to date.

Note: In the previous FTAPI Outlook Add-In, updates must be rolled out manually to all employees.

Platform support

The FTAPI Add-In was developed specifically for the new Outlook and Outlook on the Web (OWA). It is completely web-based and therefore fundamentally designed for cross-platform use.

Note: macOS is currently not supported. The FTAPI Add-In for the new Outlook is currently not available on macOS. The cause lies with Microsoft: Support was originally announced for September 2025, but is currently not being pursued further by Microsoft. FTAPI will provide information as soon as there is news on this.

General notes on the new Outlook

Data protection and the new Outlook

Before switching to the new Outlook, FTAPI generally recommends conducting a data protection review. Changes in the functions and processes of the new Outlook version may have an impact on your internal data protection policies. The Federal Commissioner for Data Protection and Freedom of Information (BfDI) offers further information and guidance on this.