Symptoms
When the "Reduce default 'referer' header granularity" feature is enabled within a browser, the post-authentication request sent to https://mail.exchange.microsoft.com/owa has a limited referrer header. Specifically, the URL path is removed. When this happens, the server skips setting six Authentication-related cookies. As a result, the user is sent back to the msft.sts.microsoft.com server to go through the Authentication flow again. The msft.sts.microsoft.com server sees that the user is logged in, and sends the user back to OWA, and the loop repeats until the server detects the loop and stops the flow.
Note The "Reduce default 'referer' header granularity" feature can be manually set by using the chrome://flags/#reduced-referrer-granularity page in Google Chrome or Microsoft Edge.
Resolution
To fix this issue, install one of the following updates:
For Exchange Server 2019, install the Cumulative Update 5 for Exchange Server 2019 or a later cumulative update for Exchange Server 2019.
For Exchange Server 2016, install the Cumulative Update 16 for Exchange Server 2016 or a later cumulative update for Exchange Server 2016.
Third-party information disclaimer
The third-party products that this article discusses are manufactured by companies that are independent of Microsoft. Microsoft makes no warranty, implied or otherwise, about the performance or reliability of these products.
References
Learn about the terminology that Microsoft uses to describe software updates.
