Outlook add-in API preview requirement set

The Outlook add-in API subset of the Office JavaScript API includes objects, methods, properties, and events that you can use in an Outlook add-in.

Preview APIs are subject to change and aren't intended for use in a production environment. We recommend that you try them out in test and development environments only. Don't use preview APIs in a production environment or within business-critical documents.

To use preview APIs:

• You must use the preview version of the Office JavaScript API library from the Office.js content delivery network (CDN). The type definition file for TypeScript compilation and IntelliSense is found at the CDN and DefinitelyTyped. You can install these types with npm install --save-dev @types/office-js-preview (be sure to remove the types for @types/office-js if you've previously installed them).

• You may need to join the Microsoft 365 Insider program for access to more recent Office builds in Outlook on Windows and on Mac.

• You may need to configure the Targeted release option on your Microsoft 365 tenant to preview features in Outlook on the web. For more information, see the "Targeted release" section of Set up the Standard or Targeted release options.

The preview requirement set includes all of the features of requirement set 1.14.

Features in preview

The following features are in preview.

Activate an event-based add-in on a message in read mode

OnMessageReadWithCustomAttachment and OnMessageReadWithCustomHeader events

Added events to activate an event-based add-in on a message in read mode when it contains certain attachment types or custom internet headers.

Available in: Classic Outlook on Windows (Microsoft 365 subscription)

HeaderName attribute in the LaunchEvent element

Added an attribute to the <LaunchEvent> XML element to specify the internet header name on which the OnMessageReadWithCustomHeader event occurs.

Available in: Classic Outlook on Windows (Microsoft 365 subscription)

MessageAttachments element

Added an XML element to specify the file extension of the attachment included in a message on which the OnMessageReadWithCustomAttachment event occurs.

Available in: Classic Outlook on Windows (Microsoft 365 subscription)

Additional calendar properties

Office.IsAllDayEvent

Added a new object that represents the all-day event property of an appointment in compose mode.

Available in: Classic Outlook on Windows (Microsoft 365 subscription)

Office.context.mailbox.item.isAllDayEvent

Added a new property that represents if an appointment is an all-day event.

Available in: Classic Outlook on Windows (Microsoft 365 subscription)

Item multi-select: Get additional message properties and run operations on multiple selected messages

Office.context.mailbox.loadItemByIdAsync

Added a new method to get additional properties and run operations on selected messages.

Available in: Classic Outlook on Windows (Microsoft 365 subscription)

Office.LoadedMessageCompose

Added a new object that represents the properties and methods of a selected message in compose mode.

Available in: Classic Outlook on Windows (Microsoft 365 subscription)

Office.LoadedMessageRead

Added a new object that represents the properties and methods of a selected message in read mode.

Available in: Classic Outlook on Windows (Microsoft 365 subscription)

Smart Alerts: Format the dialog message using Markdown

Office.SmartAlertsEventCompletedOptions.errorMessageMarkdown

Added an event.completed option to format a message in a Smart Alerts dialog using Markdown. To learn more, see the Smart Alerts walkthrough and Limitations to formatting the dialog message using Markdown.

Available in: Classic Outlook on Windows (Microsoft 365 subscription)

Temporarily set the body or subject displayed in read mode

Office.context.mailbox.item.display

Added a property that gets an object to temporarily set the content displayed in the body or subject of a message in read mode.

Available in: Classic Outlook on Windows (Microsoft 365 subscription)

Office.Display

Added an object that provides properties to temporarily set the content displayed in the body or subject of a message in read mode.

Available in: Classic Outlook on Windows (Microsoft 365 subscription)

Office.DisplayedBody

Added an object that provides a method to temporarily set the content displayed in the body of a message in read mode.

Available in: Classic Outlook on Windows (Microsoft 365 subscription)

Office.DisplayedSubject

Added an object that provides a method to temporarily set the content displayed in the subject of a message in read mode.

Available in: Classic Outlook on Windows (Microsoft 365 subscription)

See also

• Outlook add-ins
• Outlook add-in code samples
• Get started
• Requirement sets and supported clients