If you rely on custom forms built with Outlook forms designer or VBScript, you are likely wondering if New Outlook can completely replace Classic Outlook. Custom forms handle tasks like expense reports, leave requests, and inventory tracking directly inside email messages or calendar items. New Outlook, built on a web-based platform, does not support the same form engine as Classic Outlook. This article explains exactly which custom form features still work, which ones break, and what alternatives exist for moving forward.
New Outlook uses a different rendering engine that cannot load VBScript code or the traditional Outlook Forms Library. Microsoft has stated that classic custom forms will not be ported to New Outlook. This means any form that uses VBScript, custom fields with formula validation, or custom form pages will stop working when you switch. For users who only use simple custom forms with static fields and no code, the transition may be possible with adjustments. For everyone else, Classic Outlook remains the only supported environment.
This article covers the exact limitations of New Outlook for custom forms, step-by-step testing steps to evaluate your own forms, and the migration options Microsoft provides for moving to Power Apps or SharePoint-based solutions.
Key Takeaways: Custom Forms in New Outlook vs Classic Outlook
- New Outlook does not support VBScript or Outlook Forms Library: Any form with custom code or custom form pages will not load in New Outlook.
- Simple static forms may still work if rebuilt as Power Apps or SharePoint forms: Microsoft recommends migrating to Power Apps or SharePoint list forms for equivalent functionality.
- Classic Outlook will continue to be supported alongside New Outlook: You can run both clients and use Classic Outlook for forms-based workflows until a full migration is completed.
Why New Outlook Cannot Run Classic Custom Forms
New Outlook is built on the Outlook on the web framework, which uses a web-based rendering engine. This engine does not include the COM components that Classic Outlook uses to load custom forms. The Outlook Forms Library, which stores published forms, is not accessible from New Outlook. The VBScript runtime is not included in the web platform, so any form that uses VBScript for validation, automation, or dynamic field behavior will not execute.
Custom forms that rely on custom form pages defined in the Forms Designer are also unsupported. New Outlook only renders the default message, appointment, or contact pages. Any additional pages you added in the Forms Designer will not appear. The form region model used by add-ins also differs, so third-party add-ins that extend forms may not function.
Microsoft has confirmed that classic custom forms will not be added to New Outlook. The company has instead invested in Power Apps, Power Automate, and SharePoint list forms as the replacement strategy. If your organization has hundreds of custom forms, a direct migration to these platforms is required.
Steps to Test Your Custom Forms in New Outlook
Before deciding to switch, test each custom form in New Outlook. The process requires access to both Classic Outlook and New Outlook on the same machine.
- Install and switch to New Outlook
Open Classic Outlook. Look for the toggle at the top-right corner labeled “Try the new Outlook.” Click it. If you do not see the toggle, your tenant may not have the feature enabled. Contact your admin to enable the “New Outlook” rollout policy. - Open a message or item that uses a custom form
In New Outlook, open an email, appointment, or contact that was created with a custom form. The form will attempt to load, but you will likely see a blank or truncated version of the item. - Check for custom fields and form pages
Click the ellipsis menu (three dots) in the reading pane or open the item in its own window. Look for any custom fields that were added via the Forms Designer. In New Outlook, custom fields may appear as plain text with no validation or formatting. - Test any VBScript functionality
If your form uses VBScript for actions like sending confirmation emails or validating data, perform those actions. VBScript will not run, so the form will behave as if no code exists. - Check the form’s publishing location
In Classic Outlook, go to Developer > Design a Form > Open Form > look under “Personal Forms Library” or “Organizational Forms Library.” In New Outlook, there is no Forms Library browser. Forms published to these libraries are not accessible.
If Your Custom Forms Still Have Issues After Testing
New Outlook shows a blank form with no fields
This happens when the custom form uses custom form pages that replace the default page. New Outlook cannot render those pages. The only fix is to redesign the form as a Power Apps canvas app or a SharePoint list form. Export the form’s schema from Classic Outlook using the Forms Designer and rebuild the fields in Power Apps.
VBScript validation does not run
New Outlook does not execute VBScript. Remove all VBScript from your workflow. Replace it with Power Automate flows that trigger on item creation or update. For example, a flow can validate that a date field is not in the past and send an email if validation fails.
Custom form buttons and menu items are missing
Classic Outlook custom forms can add custom actions, buttons, and menu items. New Outlook does not support these customizations. Use Outlook add-ins or Power Apps to add custom buttons that perform actions like approving or rejecting a request.
New Outlook vs Classic Outlook for Custom Forms: Comparison
| Feature | New Outlook | Classic Outlook |
|---|---|---|
| VBScript support | Not supported | Fully supported |
| Outlook Forms Library (Personal and Organizational) | Not accessible | Fully supported |
| Custom form pages (additional tabs) | Not rendered | Fully supported |
| Custom fields with validation formulas | Fields visible but validation ignored | Fully supported |
| Form publishing to public folders | Not supported | Supported |
| Power Apps integration | Supported via add-ins and embedded apps | Not natively integrated |
| SharePoint list forms | Supported via browser | Supported with limited integration |
| Outlook add-in support | Fully supported | Fully supported |
| Offline form access | Limited to cached items | Full offline with Cached Exchange Mode |
Migration Options for Custom Forms
Microsoft recommends three migration paths for custom forms. The first is Power Apps, where you rebuild the form as a canvas app that can be embedded in Outlook via the Power Apps add-in. The second is SharePoint list forms, which work for forms that submit data to a list. The third is Power Automate, which replaces VBScript logic with cloud flows. None of these options are a direct one-to-one replacement, but they provide modern, supported functionality that works in New Outlook.
For forms that are used infrequently or have low complexity, you can continue using Classic Outlook alongside New Outlook. The two clients can run on the same machine. Use the toggle to switch back to Classic Outlook when you need to work with custom forms. This approach works until Microsoft eventually phases out Classic Outlook, which has no announced end date as of 2025.
You can now evaluate whether New Outlook meets your custom form requirements. Test each form using the steps above. For forms that require VBScript or custom form pages, keep Classic Outlook installed and plan a migration to Power Apps or SharePoint forms. As a practical next step, open the Forms Designer in Classic Outlook, export the form definition to a .ofs file, and review the field list to estimate the migration effort.