Assume that you have multiple Active Directory (AD) sites in a Microsoft Exchange Server 2016 environment. Then you configure the Active Directory sites by using the same external URL for the Exchange Control Panel (ECP). When you try to log on the ECP by using a mailbox that's located in a different site, the ECP redirection is failed.
This issue happens because 302 redirection response contains an incorrect path so that Exchange Server can't understand where it has to be redirected.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
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