Cisco Unity Connection and Microsoft 365 EWS Deprecation

May 12, 2026

Cisco has released Field Notice FN74365 regarding a significant upcoming change that will impact organizations using Cisco Unity Connection with Microsoft 365 Exchange Online. Microsoft is retiring Exchange Web Services (EWS) for Exchange Online beginning October 1, 2026, which means voicemail synchronization between Cisco Unity Connection and Microsoft 365 will stop functioning unless organizations take action.

What Is Changing?

Today, Cisco Unity Connection relies on Exchange Web Services (EWS) to synchronize voicemails between Unity Connection and Microsoft 365 mailboxes. This integration allows users to receive and manage voicemails directly from Outlook and other Microsoft 365 applications.

Once Microsoft officially deprecates EWS for Exchange Online, Unity Connection systems still using EWS will no longer be able to sync voicemail messages to user mailboxes.

Potential Impact

Organizations that do not upgrade before the deadline may experience:

  • Voicemails deposited in Unity Connection no longer appearing in Outlook or Microsoft 365 mailboxes
  • Disruptions to unified messaging workflows
  • Issues with voicemail playback and message synchronization
  • Potential impacts to Message Waiting Indicators (MWI)

Cisco has classified this as a High Impact issue.

Affected Products

The following Cisco Unity Connection versions are affected:

  • Cisco Unity Connection 14.x (all releases)
  • Cisco Unity Connection 15.x releases earlier than 15 SU4

This issue only affects environments integrated with Microsoft 365 / Exchange Online. On-premises Microsoft Exchange deployments are not impacted.

Recommended Solution

Cisco recommends upgrading to Cisco Unity Connection 15 SU4 or later. These releases include support for Microsoft Graph API, which replaces the deprecated EWS integration method.

Organizations currently using Unity Connection with Microsoft 365 should begin planning upgrade activities well ahead of the October 1, 2026 deadline to avoid service disruptions.

Key Takeaway

If your organization uses Cisco Unity Connection integrated with Microsoft 365 Exchange Online, proactive planning is essential. Upgrading to a Graph API-supported release before Microsoft’s EWS retirement date will ensure continued voicemail synchronization and uninterrupted unified messaging functionality.

How CAIT Can Help

If you are a current CAIT managed services client, our team is already tracking this Cisco and Microsoft change and planning the necessary remediation steps to help ensure continued voicemail synchronization functionality.

To learn more or schedule an assessment, contact the CAIT team today.

 

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