Privacy and security for mail apps in Outlook

The Office Store hosts low-trust and high-trust mail apps which can be installed by end users and administrators depending on the requested permissions. The Office Store enforces the following measures to maintain the integrity of these mail apps:

• Requires the host server of an app to always use Secure Socket Layer (SSL) to communicate.

• Requires a developer to provide proof of identity, a contractual agreement, and a compliant privacy policy to submit apps.

• Archives apps in read-only mode.

• Supports a user-review system for available apps to promote a self-policing community.

The security model addresses security, privacy, and performance concerns of end users in the following ways:

• End user’s messages that are protected by Outlook’s Information Rights Management (IRM) do not interact with mail apps.

• End users must make an explicit permission grant to install a low-trust mail app. No mail app is automatically pushed onto a client computer without manual validation by the user or administrator.

• Granting the restricted permission allows the mail app to have limited access on only the current item. Granting the read item permission allows the mail app to access personal identifiable information, such as sender and recipient names and email addresses, on only the current item,.

• End users can install a low-trust mail app for only himself or herself. Mail apps that affect an organization are installed by an administrator.

• End users can install low-trust mail apps that enable context-sensitive scenarios that are compelling to users while minimizing the users’ security risks.

• Manifest files of installed mail apps are secured in the user’s email account.

• Data communicated with servers hosting apps for Office is always encrypted according to the Secure Socket Layer (SSL) protocol.

• Applicable to only the Outlook rich client: The Outlook rich client monitors the performance of installed mail apps, exercises governance control, and disables those mail apps that exceed limits in the following areas:

  • Response time to activate.

  • Number of failures to activate or reactivate.

  • Memory usage.

  • CPU usage.

  Governance deters denial-of-service attacks and maintains app performance at a reasonable level. The Business Bar alerts end users those mail apps that the Outlook rich client has disabled based on such governance control.

• At any time, end users can disable or subsequently enable any low-trust or high-trust mail app by turning the status of a mail app off or on in the Exchange Admin Center.

The security model provides developers granular levels of permissions to choose from, and strict performance guidelines to observe. The following is a summary:

• Developers request an appropriate level of permission for a mail app, based on its need to read or write certain properties of an item, or to create and send an item.

• Developers request permission by using the Permissions element in the manifest of the mail app, by assigning a value of Restricted, ReadItem, or ReadWriteMailbox, as appropriate. The following example requests the read item permission.

  XML

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  <Permissions>ReadItem</Permissions>
  

• Developers request the restricted permission if the mail app activates on a specific type of Outlook items (appointment or message), or on specific extracted entities (phone number, address, URL) being present in the item’s subject or body. For example, the following rule activates the mail app if one or more of three entities, phone number, postal address, or URL, are found in the subject or body of the current message.

  XML

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  <Permissions>Restricted</Permissions>
      <Rule xsi:type="RuleCollection" Mode="And">
      <Rule xsi:type="ItemIs" ItemType="Message" />
      <Rule xsi:type="RuleCollection" Mode="Or">
          <Rule xsi:type="ItemHasKnownEntity" EntityType="PhoneNumber" />
          <Rule xsi:type="ItemHasKnownEntity" EntityType="Address" />
          <Rule xsi:type="ItemHasKnownEntity" EntityType="Url" />
      </Rule>
  </Rule>
  

• Developers request the read item permission if the mail app needs to read properties of the current item other than the default extracted entities, or write custom properties set by the app on the current item, but does not require reading or writing to other items, or creating or sending a message in the user’s mailbox. For example, a developer should request read item permission if a mail app needs to look for an entity like a meeting suggestion, task suggestion, email address, or contact name in the item’s subject or body, or uses a regular expression to activate.

• Developers request the read/write mailbox permission only if the mail app needs to do one or more of the following actions by using the makeEWSRequestAsync method of the Mailbox object (apps for Office) object:

  • Read or write to properties of items in the mailbox.

  • Create, read, write, or send items in the mailbox.

  • Create, read, or write to folders in the mailbox.

  Only administrators can install mail apps that require this permission. For more information about permissions, see Using the permission model for mail apps in Outlook.

• Developers must incorporate performance tuning in their development workflow. They should follow the guidelines in designing activation rules as described in Limits for activation and data in mail apps for Outlook. If a mail app is intended to run on the Outlook rich client, then developers should verify that the app performs within the resource usage limits, as described in Following resource usage rules in apps for Office.

• Developers cannot use ActiveX controls in apps because they are not supported.

• Developers should do the following when submitting a mail app to the Office Store:

  • Produce an Extended Validation (EV) SSL certificate as a proof of identity.

  • Host the app they are submitting on a web server that supports SSL.

  • Produce a compliant privacy policy.

  • Be ready to sign a contractual agreement upon submitting the app.

The security model provides the following rights and responsibilities to administrators:

• Can install low-trust and high-trust mail apps, including those that require read/write mailbox permission and provide richer access to mailboxes.

• Granting the read/write mailbox permission allows a mail app to access personal identifiable information on all items in the user’s mailbox, and read or modify any item in the mailbox.

• Can prevent end users from installing any mail app, including apps on the Office Store.

• Can disable or enable any mail app on the Exchange Admin Center.

• Applicable to only the Outlook rich client: Can override performance threshold settings by GPO registry settings. For more information, see Overriding resource usage settings for performance of apps for Office.