The Hybrid Calendar provides a rich collaboration experience between Cisco Webex Meetings and Webex App with Microsoft Exchange or Office 365, for users and rooms.

Currently, the integration provides the following major features:

  1. Provide end users the ability to schedule a collaboration meeting with any calendar client connected to Microsoft Exchange or Office 365 without having to install plug-ins or extensions. Just type a keyword into the Location field (for example, @webex or @meet) or put a SIP URI or meeting address into the meeting body.

  2. Show a meetings list in users' Webex App applications—desktop, mobile, and hard endpoints.

  3. Pop up a notification with a Join button, also known as One Button to Push (OBTP).

  4. Update a user’s Webex App presence status when the user sets up automatic replies in Outlook (sometimes referred to as out-of-office status).

This article gives an overview of how the Expressway-based Calendar Connector integrates on-premises Microsoft Exchange (and, optionally, Office 365) with the Webex cloud to provide these features.

For similar overviews of the other Hybrid Calendar Service integrations, see the following articles:

For the latest feature and deployment information, see https:/​/​​go/​hybrid-services-calendar.

Data handling

The Hybrid Calendar receives meeting details from the calendar system and parses the meeting location and body for URIs and URLs that can be used to join the meetings. The service uses other information, such as start and end time and invitees, to populate the meetings list in the Webex App app and on certain devices, and to provide One Button to Push (OBTP). At no point does the service store or send unencrypted sensitive data such as meeting description, meeting body, or email addresses of invitees. That data is sent encrypted to the Webex cloud (and stored there in encrypted form) for the purposes of providing the meetings list and OBTP.

For data encryption, the Hybrid Calendar uses the same Webex cloud encryption service that the Webex App app uses. As such, key management is provided either by the cloud Key Management Server (KMS), or, if you choose to deploy Hybrid Data Security, by your own on-premises KMS. (For more details, see the Webex App Security Paper.)

Authentication and authorization during deployment

calendar connector integrates Webex with Microsoft Exchange 2013, 2016, 2019 or Office 365 through an impersonation account. The application impersonation management role in Exchange enables applications to impersonate users in an organization to perform tasks on behalf of the user. The application impersonation role must be configured in Exchange and is used in the calendar connector as part of the Exchange configuration on the Expressway-C interface.

The Exchange impersonation account is Microsoft's recommended method for this task. Expressway-C administrators don't need to know the password, because the value can be entered in the Expressway-C interface by an Exchange administrator. The password isn't clearly shown, even if the Expressway-C administrator has root access to the Expressway-C box. The password is stored encrypted using the same credential encryption mechanism as other passwords on the Expressway-C.

For additional security, follow the steps in the Deployment Guide for Webex Hybrid Calendar Service to enable TLS in order to secure EWS connections on the wire.

Provisioning process

Ongoing operations

The Hybrid Calendar uses Exchange Web Services (EWS) to access Microsoft Exchange and Office 365 calendar events. EWS supports a broad range of mailbox operations. However, the Hybrid Calendar uses only a subset of commands that are related to calendar use cases.

Table 1. Operations currently used by Hybrid Calendar Service

EWS operation



Simple connectivity check.


Search for events in a user's calendar.


Retrieve details about a calendar folder.


Retrieve details about events in a calendar folder.


Receive streaming notifications on calendar events.


Retrieve a user's out-of-office settings.


Subscribe for notifications on changes to a user's calendar.


Detect changed meetings when not subscribed (missed, upgrades, and so on).


Unsubscribe from notifications on changes to a user's calendar.


Update properties of calendar events (including join information and extended properties).


Create a new meeting request based on the input the user provides in the Webex client. New meetings are created both organizers and users based on their availability.


Displays the user availability and free/busy status for a specified time range.

The Hybrid Calendar also makes periodic calls to the Autodiscover service to locate user mailboxes.