Symptoms
After you install Microsoft Exchange Server 2019 Cumulative Update 10 (CU10) or Microsoft Exchange Server 2016 CU21, additions or changes to custom attributes that are made in the Exchange admin center (EAC) are not saved. The same operations work successfully in Exchange Server 2019 CU9 and Exchange Server 2016 CU20.
Workaround
To edit the custom attribute values, use one of the following workarounds.
Workaround 1
Use EAC in Internet Explorer.
Workaround 2
Use the Exchange Management Shell.
Status
Microsoft is researching this problem and will post more information in this article when the information becomes available.
