New Outlook for Windows - Replacement for Microsoft.Office.Interop.Outlook COM API

Mark Joseph Evasco 0 Reputation points
2026-08-31T16:58:11.6866667+00:00

Hello Team,

We are currently investigating an issue related to Outlook integration in our application.

Our application uses Microsoft.Office.Interop.Outlook (COM Interop) to perform Outlook-related operations. We have observed that after users migrate to New Outlook for Windows, the existing functionality no longer works, as COM-based Outlook automation appears to be unavailable in the new client.

We are reviewing a process related to the removal of GI Rules, and we need guidance on the recommended Microsoft-supported approach moving forward.

Could you please help clarify the following:

  1. Is Microsoft.Office.Interop.Outlook officially unsupported in New Outlook for Windows?
  2. If COM Interop is no longer supported, what is the Microsoft-recommended replacement?
  3. Are there migration guides or best practices available for applications currently using Outlook COM automation?
  4. For functionality that previously relied on Outlook Interop, such as:
    • Creating email messages
    • Opening draft emails for user review
    • Accessing Outlook folders/mail items
    • Processing email-based workflows
    What is the recommended implementation pattern in New Outlook?
  5. Has Microsoft provided any roadmap or guidance for organizations transitioning from Classic Outlook to New Outlook when COM-based integrations are involved?

Any guidance or documentation references would be greatly appreciated.

Thank you.

Microsoft 365 and Office | Other
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  1. AI answer

    2026-08-31T16:58:34.2966667+00:00

    Yes. Microsoft.Office.Interop.Outlook and other COM-based Outlook extensibility are not supported in new Outlook for Windows.

    Supported status in new Outlook:

    • COM add-ins: not supported
    • Outlook Object Model (OOM): not supported
    • MAPI: not supported
    • VBA and Macros: not supported
    • Web add-ins: supported

    Recommended replacement

    • For UI-integrated Outlook extensions, move from COM add-ins to web add-ins.
    • For automation and mailbox operations, use:
      • Microsoft Graph for sending mail, reading/processing messages, and mailbox workflows
      • Office.js APIs for Outlook-integrated add-in scenarios
      • Power Automate for cross-app and email workflow automation

    Recommended implementation pattern for the scenarios listed:

    • Creating email messages: use Microsoft Graph or an Outlook web add-in, depending on whether the scenario is backend automation or in-client UI.
    • Opening draft emails for user review: implement this through an Outlook web add-in using Office.js APIs for client-side integration.
    • Accessing Outlook folders/mail items: use Microsoft Graph for mailbox data access and processing.
    • Processing email-based workflows: use Microsoft Graph and/or Power Automate.

    Migration guidance and best practices

    • Microsoft provides guidance to migrate from COM add-ins to web add-ins.
    • If an existing COM add-in has a web add-in counterpart, users can be offered installation of that counterpart when switching to new Outlook.
    • If a counterpart is not listed, search the Microsoft commercial marketplace or confirm with the vendor whether a private web add-in exists.
    • Organizations are advised to inventory existing COM add-ins and plan replacements before migration.

    Transition guidance for organizations

    • Microsoft’s guidance is to use the migration period to identify COM add-ins, validate blockers, and transition to web add-ins.
    • New Outlook does not support COM-based integrations, so organizations with COM dependencies should plan migration before broad rollout.
    • For pilot users, capture which workflows require classic Outlook because of missing functionality.

    A practical transition approach is:

    1. Inventory current COM add-ins and Outlook automation dependencies.
    2. Classify each dependency as:
      • UI extension inside Outlook → web add-in / Office.js
      • Mailbox automation or workflow → Microsoft Graph / Power Automate
    3. Check whether vendor add-ins already have web add-in replacements.
    4. Keep affected users on classic Outlook until the replacement path is implemented.
    AI-generated content may be incorrect. Read our transparency notes for more information.

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