Remote Connectivity Analyzer Diagnoses Teams Connections to Exchange Hybrid

Bringing RCA Back to Life

For many years, the Microsoft Remote Connectivity Analyzer (MRCA) was in the doldrums. No Microsoft engineering group wanted to take responsibility for its development and maintenance, and issues like expiring certificates occurred all the time. RCA was not in good shape and not much happened between October 2015 and January 2020.

The history of RCA is that it started in 2009 as the Exchange Remote Connectivity Analyzer (ExRCA), a utility program to help Microsoft support and Exchange administrators debug connectivity problems. At the time, Exchange server handled protocols like Exchange ActiveSync (mobile), Exchange Web Services, Outlook Anywhere (RPC over HTTP), and SMTP, with tests later appearing for POP3 and IMAP4. ExRCA was very popular and boasted its own Twitter account and YouTube video (a real trip into the past).

In 2011, Microsoft updated ExRCA to support Office 365, but its focus remained firmly fixed on Exchange (the URL at the time was However, Microsoft dropped some hints that they wanted to incorporate connectivity tests for other applications than Exchange. Those plans and other ideas for enhancements foundered due to a lack of investment and engineering availability.

Debugging Teams and Exchange Hybrid

Despite the five year hiatus, the good news is that MRCA is better than ever before. It has a new lease of life and backing within Microsoft that has allowed its developers to create new tests to help Microsoft 365 tenant administrators figure out when connectivity goes wrong. The latest tests, revealed in a Microsoft technical community post of March 3, analyze the connections between Teams and an Exchange hybrid environment.

Teams works best when it interacts with an Exchange Online mailbox. However, as we know, many on-premises Exchange servers still host mailboxes, and given the success of Teams, it’s likely that millions of Teams users have on-premises mailboxes. Microsoft documents what how Teams and Exchange interact and issues that occur between Teams and Exchange Server. Over the years, connectivity has become smoother as customers upgraded to Exchange 2016 CU3 or later (always upgrade to the latest cumulative update to avoid problems like last year’s Hafnium debacle).

The latest MRCA diagnostic test for Teams-Exchange connectivity (Figure 1) checks the common problems known to exist and validates that the Exchange hybrid configuration is correct for Teams users.

The set of Teams diagnostics in the Remote Connectivity Analyzer
Figure 1: The set of Teams diagnostics in the Remote Connectivity Analyzer

Running the test is simple. All that’s needed is the user principal name of a Teams user. You are asked to sign into the account, and thereafter the diagnostics exercise different aspects of connectivity to identify any lurking issues (Figure 2).

The Remote Connectivity Analyzer completes Teams diagnostics
Figure 2: The Remote Connectivity Analyzer completes Teams diagnostics

The REST Reference

Everything looks good. The only nagging doubt I had is the reference to checking the EWS and REST endpoints for Exchange Server. Twenty-seven minutes after announcing the new MRCA tests for Teams, Microsoft said that they plan to remove support for the REST API for on-premises mailboxes in March 2023. Microsoft introduced REST API access to mailboxes as a preview feature in Exchange 2016 CU3. The API never progressed from its preview status, which means that it was always liable for discontinuation. When the axe descends next year, Exchange will block requests made via the REST API. EWS continues and remains the approved method for programmatic access to Exchange server mailboxes.

The MRCA developers point to the need to check the REST endpoint, so does this imply that the Teams hybrid connection to Exchange Server uses the REST API? I guess all will become clear in time and, if necessary, the MRCA developers will make the necessary adjustment as they continue to develop this valuable and worthwhile utility.

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