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Get and set add-in metadata for an Outlook add-in

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Manage custom data in your Outlook add-in by using either of the following:

  • Roaming settings, which manage custom data for a user's mailbox.
  • Custom properties, which manage custom data for an item in a user's mailbox.

Both of these give access to custom data that's only accessible by your Outlook add-in, but each method stores the data separately from the other. That is, the data stored through roaming settings isn't accessible by custom properties, and vice versa. Roaming settings are stored on the user's mailbox while custom properties are stored on a message or appointment. Stored data is accessible in subsequent Outlook sessions on all the form factors that the add-in supports.

Custom data per mailbox: roaming settings

You can specify data specific to a user's Exchange mailbox using the RoamingSettings object. Examples of such data include the user's personal data and preferences. Your mail add-in can access roaming settings when it roams on any device it's designed to run on (desktop, tablet, or smartphone).

Changes to this data are stored on an in-memory copy of those settings for the current Outlook session. You should explicitly save all the roaming settings after updating them so that they'll be available the next time the user opens your add-in, on the same or any other supported device.

Roaming settings format

The data in a RoamingSettings object is stored as a serialized JavaScript Object Notation (JSON) string.

The following is an example of the structure, assuming there are three defined roaming settings named add-in_setting_name_0, add-in_setting_name_1, and add-in_setting_name_2.

{
  "add-in_setting_name_0": "add-in_setting_value_0",
  "add-in_setting_name_1": "add-in_setting_value_1",
  "add-in_setting_name_2": "add-in_setting_value_2"
}

Loading roaming settings

A mail add-in typically loads roaming settings in the Office.initialize event handler. The following JavaScript code example shows how to load existing roaming settings and get the values of two settings, customerName and customerBalance.

let _mailbox;
let _settings;
let _customerName;
let _customerBalance;

// The initialize function is required for all add-ins.
Office.initialize = function () {
  // Initialize instance variables to access API objects.
  _mailbox = Office.context.mailbox;
  _settings = Office.context.roamingSettings;
  _customerName = _settings.get("customerName");
  _customerBalance = _settings.get("customerBalance");
}

Creating or assigning a roaming setting

Continuing with the preceding example, the following JavaScript function, setAddInSetting, shows how to use the RoamingSettings.set method to set a setting named cookie with today's date, and persist the data by using the RoamingSettings.saveAsync method to save all the roaming settings to the user's mailbox.

The set method creates the setting if the setting doesn't already exist, and assigns the setting to the specified value. The saveAsync method saves roaming settings asynchronously. This code sample passes a callback function, saveMyAddInSettingsCallback, to saveAsync. When the asynchronous call finishes, saveMyAddInSettingsCallback is called by using one parameter, asyncResult. This parameter is an AsyncResult object that contains the result of and any details about the asynchronous call. You can use the optional userContext parameter to pass any state information from the asynchronous call to the callback function.

// Set a roaming setting.
function setAddInSetting() {
  _settings.set("cookie", Date());
  // Save roaming settings to the mailbox, so that they'll be available in the next session.
  _settings.saveAsync(saveMyAddInSettingsCallback);
}

// Callback function after saving custom roaming settings.
function saveMyAddInSettingsCallback(asyncResult) {
  if (asyncResult.status == Office.AsyncResultStatus.Failed) {
    // Handle the failure.
  }
}

Removing a roaming setting

Also extending the preceding examples, the following JavaScript function, removeAddInSetting, shows how to use the RoamingSettings.remove method to remove the cookie setting and save all the roaming settings to the mailbox.

// Remove an add-in setting.
function removeAddInSetting()
{
  _settings.remove("cookie");
  // Save changes to the roaming settings for the mailbox, so that they'll be available in the next session.
  _settings.saveAsync(saveMyAddInSettingsCallback);
}

Custom data per item in a mailbox: custom properties

You can specify data specific to an item in the user's mailbox using the CustomProperties object. For example, your mail add-in could categorize certain messages and note the category using a custom property messageCategory. Or, if your mail add-in creates appointments from meeting suggestions in a message, you can use a custom property to track each of these appointments. This ensures that if the user opens the message again, your mail add-in doesn't offer to create the appointment a second time.

Similar to roaming settings, changes to custom properties are stored on in-memory copies of the properties for the current Outlook session. To make sure these custom properties will be available in the next session, use CustomProperties.saveAsync.

These add-in-specific, item-specific custom properties can only be accessed by using the CustomProperties object. These properties are different from the custom, MAPI-based UserProperties in the Outlook object model, and extended properties in Exchange Web Services (EWS). You can't directly access CustomProperties by using the Outlook object model, EWS, or Microsoft Graph. To learn how to access CustomProperties using Microsoft Graph or EWS, see the section Get custom properties using Microsoft Graph or EWS.

Note

Custom properties are only available to the add-in that created them and only through the mail item in which they were saved. Because of this, properties set while in compose mode aren't transmitted to recipients of the mail item. When a message or appointment with custom properties is sent, its properties can be accessed from the item in the Sent Items folder. To allow recipients to receive the custom data your add-in sets, consider using InternetHeaders instead.

Using custom properties

Before you can use custom properties, you must load them by calling the loadCustomPropertiesAsync method. After you've created the property bag, you can use the set and get methods to add and retrieve custom properties. You must use the saveAsync method to save any changes that you make to the property bag.

Note

When using custom properties in Outlook add-ins, keep in mind that:

  • Outlook on Mac doesn't cache custom properties. If the user's network goes down, add-ins in Outlook on Mac wouldn't be able to access their custom properties.
  • In classic Outlook on Windows, custom properties saved while in compose mode only persist after the item being composed is closed or after Office.context.mailbox.item.saveAsync is called.

Custom properties example

The following example shows a simplified set of functions and methods for an Outlook add-in that uses custom properties. You can use this example as a starting point for your add-in that uses custom properties.

This example includes the following functions and methods.

  • Office.initialize -- Initializes the add-in and loads the custom property bag from the Exchange server.

  • customPropsCallback -- Gets the custom property bag that's returned from the server and saves it locally for later use.

  • updateProperty -- Sets or updates a specific property, and then saves the change to the local property bag.

  • removeProperty -- Removes a specific property from the property bag, and then saves these changes.

let _mailbox;
let _customProps;

// The initialize function is required for all add-ins.
Office.initialize = function () {
  _mailbox = Office.context.mailbox;
  _mailbox.item.loadCustomPropertiesAsync(customPropsCallback);
}

// Callback function from loading custom properties.
function customPropsCallback(asyncResult) {
  if (asyncResult.status == Office.AsyncResultStatus.Failed) {
    // Handle the failure.
  }
  else {
    // Successfully loaded custom properties,
    // can get them from the asyncResult argument.
    _customProps = asyncResult.value;
  }
}

// Get individual custom property.
function getProperty() {
  const myProp = _customProps.get("myProp");
}

// Set individual custom property.
function updateProperty(name, value) {
  _customProps.set(name, value);
  // Save all custom properties to the mail item.
  _customProps.saveAsync(saveCallback);
}

// Remove a custom property.
function removeProperty(name) {
  _customProps.remove(name);
  // Save all custom properties to the mail item.
  _customProps.saveAsync(saveCallback);
}

// Callback function from saving custom properties.
function saveCallback() {
  if (asyncResult.status == Office.AsyncResultStatus.Failed) {
    // Handle the failure.
  }
}

Get custom properties using Microsoft Graph or EWS

To get CustomProperties using Microsoft Graph or EWS, you should first determine the name of its MAPI-based extended property. You can then get that property in the same way you would get any MAPI-based extended property.

The use of Microsoft Graph or EWS depends on the type of Exchange environment in which the add-in runs. Select the applicable tab for your environment.

In Exchange Online environments, your add-in can construct a Microsoft Graph request against messages and events to get the ones that already have custom properties. In your request, you should include the CustomProperties MAPI-based property and its property set using the details provided in How custom properties are stored on an item.

The following example shows how to get all events that have any custom properties set by your add-in. It also ensures that the response includes the value of the property, so you can apply further filtering logic.

Important

In the following example, replace <app-guid> with your add-in's ID.

GET https://graph.microsoft.com/v1.0/me/events?$filter=singleValueExtendedProperties/Any
  (ep: ep/id eq 'String {00020329-0000-0000-C000-000000000046}
  Name cecp-<app-guid>' and ep/value ne null)
  &$expand=singleValueExtendedProperties($filter=id eq 'String
  {00020329-0000-0000-C000-000000000046} Name cecp-<app-guid>')

For other examples that get single-value MAPI-based extended properties, see Get singleValueLegacyExtendedProperty.

Tip

To learn how to obtain an access code to Microsoft Graph, see Enable SSO in an Office Add-in using nested app authentication (preview).

How custom properties are stored on an item

Custom properties set by an add-in aren't equivalent to normal MAPI-based properties. Add-in APIs serialize all your add-in's CustomProperties as a JSON payload and then save them in a single MAPI-based extended property whose name is cecp-<app-guid> (<app-guid> is your add-in's ID) and property set GUID is {00020329-0000-0000-C000-000000000046}. (For more information about this object, see MS-OXCEXT 2.2.5 Mail App Custom Properties.) You can then use Microsoft Grpah or EWS to get this MAPI-based property.

Platform behavior in messages

The following table summarizes saved custom properties behavior in messages for various Outlook clients.

Scenario Outlook on the web and on new Windows client classic Outlook on Windows Outlook on Mac
New compose null null null
Reply, reply all null null null
Forward null Loads parent's properties null
Sent item from new compose null null null
Sent item from reply or reply all null null null
Sent item from forward null Removes parent's properties if not saved null

To handle the situation in classic Outlook on Windows:

  1. Check for existing properties on initializing your add-in, and keep them or clear them as needed.
  2. When setting custom properties, include an additional property to indicate whether the custom properties were added in read mode. This will help you differentiate if the property was created in compose mode or inherited from the parent.
  3. To check if the user is forwarding or replying to a message, you can use item.getComposeTypeAsync (available from requirement set 1.10).

See also