Microsoft has confirmed a Windows Server bug that can break Active Directory schema replication when the forest Schema Master FSMO role is hosted on a Windows Server 2025 domain controller and an Exchange schema change is applied, producing schema‑mismatch replication errors that can rapidly...
Microsoft and Exchange teams are warning administrators about a narrow—but potentially high‑impact—Active Directory schema replication problem that can surface when an Exchange cumulative update (for example, Exchange 2019 CU15 or Exchange Server Subscription Edition RTM) extends the schema...
A subtle but dangerous bug in Windows Server 2025’s Schema Master FSMO role is causing duplicate schema entries that can break Active Directory replication and trigger schema-mismatch errors on older domain controllers — the issue is being discussed by administrators and reported in the field...
active directory
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domain controllers
event id 1203
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fsmo roles
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schema master
schema mismatch
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windows server 2025