Create Single-Value Extended Property

You can add custom data to an Outlook email message by creating a single-value MAPI extended property via a Graph API POST request to the messages endpoint. This attaches custom metadata to individual emails beyond standard fields.

A single-value MAPI extended property in Microsoft Graph is a custom data field used to store user-defined information on Outlook messages. It enables richer data association for emails when standard Graph API fields are insufficient.

To tag an Outlook message with a project code using the Graph API, create a single-value extended property by sending a POST request with the message ID, a property identifier, and the project code value.

Creating an extended property on an Outlook message requires the specific message ID, a property identifier defining the custom field, and the property value you want to store. These are sent via a POST request to the messages endpoint.

Yes, you can use the Microsoft Graph API to store custom metadata not natively supported by Outlook by creating single-value MAPI extended properties. This method augments messages with specific user-defined data points like customer satisfaction ratings.

Use MAPI extended properties instead of standard Outlook fields when you need to attach specific, user-defined data points to individual emails. This approach provides enhanced metadata capabilities for data not natively supported by the Graph API.