Important update for customers using the authenticated SMTP connector with Microsoft Exchange

Microsoft Exchange Online is retiring Basic authentication for Client Submission (SMTP AUTH) starting at the end of December, 2026. This change impacts Zendesk customers using the authenticated SMTP connector with Microsoft Exchange.

If your business uses the authenticated SMTP connector with other email providers, such as Google or Yahoo, this announcement doesn't apply to you and can be safely ignored.

This announcement includes the following topics:

What's happening?

What do I need to do?

What are my alternative options?

What's happening?

At the end of December, 2026, Exchange Online will begin to phase out Basic auth for SMTP submission, with 100% enforcement in 2027. After that time, any application or device using Basic auth with SMTP will be unable to send email through Exchange Online.

The authenticated SMTP connector uses Basic auth for connections with Microsoft services. Therefore, Zendesk customers using the authenticated SMTP connector with Microsoft Exchange are impacted by this change.

What do I need to do?

To avoid disruptions, customers currently using the SMTP connector with Microsoft Exchange should migrate support addresses to the Exchange connector, which supports modern OAuth authentication.  The process for connecting support addresses through the Exchange Connector is detailed in Connecting your Microsoft Exchange account to Zendesk. You can identify the support addresses using the authenticated SMTP connector in the Domains section of your Email settings.

Review your current setup and plan to migrate your email submission method to the Exchange Connector before December 2026 to ensure uninterrupted email delivery.

For full details and step-by-step instructions, see Microsoft’s official announcement on the Deprecation of Basic Authentication in Exchange Online.

For more information about the Exchange Connector, including limitations and requirements, see About the Exchange Connector.

What are my alternative options?

Alternative options are described in more detail in Microsoft's announcement. Some of those options include:

Leveraging High Volume Email for Microsoft 365 for internal recipients

Adopting Azure Communication Services Email for internal and external recipients

For hybrid setups, authenticating with an on-premises Exchange Server or configuring it for anonymous relay

Thank you for partnering with Zendesk to keep your email secure and reliable.

If you have feedback or questions related to this announcement, visit our community forum where we collect and manage customer product feedback. For general assistance with your Zendesk products, contact Zendesk Customer Support.