Match strings in an Outlook item as well-known entities

Before sending a message or meeting request item, Exchange Server parses the contents of the item, identifies and stamps certain strings in the subject and body that resemble entities well-known to Exchange, for example, email addresses, phone numbers, and URLs. Messages and meeting requests are delivered by Exchange Server in an Outlook Inbox with well-known entities stamped.


Entity-based contextual Outlook add-ins will be retired in Q2 of 2024. The work to retire this feature will start in May and continue until the end of June. After June, contextual add-ins will no longer be able to detect entities in mail items to perform tasks on them. The following APIs will also be retired.

To help minimize potential disruptions, the following will still be supported after entity-based contextual add-ins are retired.

  • An alternative implementation of the Join button, which is activated by online meeting add-ins, is being developed. Once support for entity-based contextual add-ins ends, online meeting add-ins will automatically transition to the alternative implementation to activate the Join button. During the transition to this implementation, the Join button may not be visible when using an online meeting add-in. As a workaround, you must select the meeting link from the body of the meeting invitation to join the meeting directly.
  • Regular expression rules will continue to be supported after entity-based contextual add-ins are retired. We recommend updating your contextual add-in to use regular expression rules as an alternative solution. For guidance on how to implement these rules, see Use regular expression activation rules to show an Outlook add-in.

For more information, see Retirement of entity-based contextual Outlook add-ins.

Using the Office JavaScript API, you can get these strings that match specific well-known entities for further processing. You can also specify a well-known entity in a rule in the add-in manifest so that Outlook can activate your add-in when the user is viewing an item that contains matches for that entity. You can then extract and take action on matches for the entity.


Outlook add-in features that depend on activation rules aren't supported when the add-in uses a Unified manifest for Microsoft 365.

Being able to identify or extract such instances from a selected message or appointment is convenient. For example, you can build a reverse phone look-up service as an Outlook add-in. The add-in can extract strings in the item subject or body that resemble a phone number, do a reverse lookup, and display the registered owner of each phone number.

This topic introduces these well-known entities, shows examples of activation rules based on well-known entities, and how to extract entity matches independently of having used entities in activation rules.

Support for well-known entities

Exchange Server stamps well-known entities in a message or meeting request item after the sender sends the item and before Exchange delivers the item to the recipient. Therefore, only items that have gone through transport in Exchange are stamped, and Outlook can activate add-ins based on these stamps when the user is viewing such items. On the contrary, when the user is composing an item or viewing an item that is in the Sent Items folder, because the item has not gone through transport, Outlook cannot activate add-ins based on well-known entities.

Similarly, you cannot extract well-known entities in items that are being composed or in the Sent Items folder, as these items have not gone through transport and are not stamped. For additional information about the kinds of items that support activation, see Activation rules for Outlook add-ins.

The following table lists the entities that Exchange Server and Outlook support and recognize (hence the name "well-known entities"), and the object type of an instance of each entity. The natural language recognition of a string as one of these entities is based on a learning model that has been trained on a large amount of data. Therefore, the recognition is non-deterministic. See Tips for using well-known entities for more information about conditions for recognition.

Entity type Conditions for recognition Object type
Address United States street addresses. For example, "1234 Main Street, Redmond, WA 07722". Generally, for an address to be recognized, it should follow the structure of a United States postal address, with most of the elements of a street number, street name, city, state, and zip code present. The address can be specified in one or multiple lines. JavaScript String object
Contact A reference to a person's information as recognized in natural language. The recognition of a contact depends on the context. For example, a signature at the end of a message, or a person's name appearing in the vicinity of some of the following information: a phone number, address, email address, and URL. Contact object
EmailAddress SMTP email addresses. JavaScript String object
MeetingSuggestion A reference to an event or meeting. For example, Exchange would recognize the following text as a meeting suggestion: "Let's meet tomorrow for lunch." MeetingSuggestion object
PhoneNumber United States telephone numbers. For example, (235) 555-0110. PhoneNumber object
TaskSuggestion Actionable sentences in an email. For example, "Please update the spreadsheet." TaskSuggestion object
Url A web address that explicitly specifies the network location and identifier for a web resource. Exchange Server does not require the access protocol in the web address, and does not recognize URLs that are embedded in link text as instances of the Url entity. Exchange Server can match the following examples: JavaScript String object

The following figure describes how Exchange Server and Outlook support well-known entities for add-ins, and what add-ins can do with well-known entities. See Retrieving entities in your add-in and Activating an add-in based on the existence of an entity for more details on how to use these entities.

Support and use of well-known entities in an Outlook add-in.

Permissions to extract entities

To extract entities in your JavaScript code or to have your add-in activated based on the existence of certain well-known entities, make sure you have requested the appropriate permissions in the add-in manifest.

Specifying the default restricted permission allows your add-in to extract the Address, MeetingSuggestion, or TaskSuggestion entity. To extract any of the other entities, specify read item, read/write item, or read/write mailbox permission in the manifest.

The following example requests the read item permission in the manifest.


To learn more about Outlook add-in permissions, see Understanding Outlook add-in permissions.

Retrieving entities in your add-in

As long as the subject or body of the item that is being viewed by the user contains strings that Exchange and Outlook can recognize as well-known entities, these instances are available to add-ins. They are available even if an add-in is not activated based on well-known entities. With the appropriate permission, you can use the getEntities or getEntitiesByType method to retrieve well-known entities that are present in the current message or appointment.

The getEntities method returns an array of Entities objects that contains all the well-known entities in the item.

If you're interested in a particular type of entities, use the getEntitiesByTypemethod which returns an array of only the entities you want. The EntityType enumeration represents all the types of well-known entities you can extract.

After calling getEntities, you can then use the corresponding property of the Entities object to obtain an array of instances of a type of entity. Depending on the type of entity, the instances in the array can be just strings, or can map to specific objects.

As an example seen in the earlier figure, to get addresses in the item, access the array returned by getEntities().addresses[]. The Entities.addresses property returns an array of strings that Outlook recognizes as postal addresses. Similarly, the Entities.contacts property returns an array of Contact objects that Outlook recognizes as contact information. Tables 1 lists the object type of an instance of each supported entity.

The following example shows how to retrieve any addresses found in a message.

// Get the address entities from the item.
const entities = Office.context.mailbox.item.getEntities();
// Check to make sure that address entities are present.
if (null != entities && null != entities.addresses && undefined != entities.addresses) {
   //Addresses are present, so use them here.

Activating an add-in based on the existence of an entity

Another way to use well-known entities is to have Outlook activate your add-in based on the existence of one or more types of entities in the subject or body of the currently viewed item. You can do so by specifying an ItemHasKnownEntity rule in the add-in manifest. The EntityType simple type represents the different types of well-known entities supported by ItemHasKnownEntity rules. After your add-in is activated, you can also retrieve the instances of such entities for your purposes, as described in the previous section Retrieving entities in your add-in.

You can optionally apply a regular expression in an ItemHasKnownEntity rule, so as to further filter instances of an entity and have Outlook activate an add-in only on a subset of the instances of the entity. For example, you can specify a filter for the street address entity in a message that contains a Washington state zip code beginning with "98". To apply a filter on the entity instances, use the RegExFilter and FilterName attributes in the Rule element of the ItemHasKnownEntity type.

Similar to other activation rules, you can specify multiple rules to form a rule collection for your add-in. The following example applies an "AND" operation on 2 rules: an ItemIs rule and an ItemHasKnownEntity rule. This rule collection activates the add-in whenever the current item is a message and Outlook recognizes an address in the subject or body of that item.

<Rule xsi:type="RuleCollection" Mode="And">
   <Rule xsi:type="ItemIs" ItemType="Message" />
   <Rule xsi:type="ItemHasKnownEntity" EntityType="Address" />

The following example uses getEntitiesByType of the current item to set a variable addresses to the results of the preceding rule collection.

const addresses = Office.context.mailbox.item.getEntitiesByType(Office.MailboxEnums.EntityType.Address);

The following ItemHasKnownEntity rule example activates the add-in whenever there is a URL in the subject or body of the current item, and the URL contains the string "youtube", regardless of the case of the string.

<Rule xsi:type="ItemHasKnownEntity" 

The following example uses getFilteredEntitiesByName(name) of the current item to set a variable videos to get an array of results that match the regular expression in the preceding ItemHasKnownEntity rule.

const videos = Office.context.mailbox.item.getFilteredEntitiesByName(youtube);

Tips for using well-known entities

There are a few facts and limits you should be aware of if you use well-known entities in your add-in. The following applies as long as your add-in is activated when the user is reading an item which contains matches of well-known entities, regardless of whether you use an ItemHasKnownEntity rule.

  • You can extract strings that are well-known entities only if the strings are in English.

  • You can extract well-known entities from the first 2,000 characters in the item body, but not beyond that limit. This size limit helps balance the need for functionality and performance, so that Exchange Server and Outlook aren't bogged down by parsing and identifying instances of well-known entities in large messages and appointments. Note that this limit is independent of whether the add-in specifies an ItemHasKnownEntity rule. If the add-in does use such a rule, note also the rule processing limit for Outlook on Windows and on Mac later in this section.

  • You can extract entities from appointments that are meetings organized by someone other than the mailbox owner. You can't extract entities from calendar items that aren't meetings, or meetings organized by the mailbox owner.

  • You can extract entities of the MeetingSuggestion type from only messages, but not appointments.

  • You can extract URLs that exist explicitly in the item body, but not URLs that are embedded in hyperlinked text in HTML item body. Consider using an ItemHasRegularExpressionMatch rule instead to get both explicit and embedded URLs. Specify BodyAsHTML as the PropertyName, and a regular expression that matches URLs as the RegExValue.

  • You can't extract entities from items in the Sent Items folder.

In addition, the following applies if you use an ItemHasKnownEntity rule, and may affect the scenarios where you'd otherwise expect your add-in to be activated.

  • When using the ItemHasKnownEntity rule, expect Outlook to match entity strings in only English regardless of the default locale specified in the manifest.

  • When your add-in is running in Outlook on Windows or on Mac, expect Outlook to apply the ItemHasKnownEntity rule to the first megabyte of the item body and not to the rest of the body over that limit.

  • You can't use an ItemHasKnownEntity rule to activate an add-in for items in the Sent Items folder.

See also