ERROR_DS_RESERVED_MAPI_ID - 8631 (0x21B7)
Schema update failed: The MAPI identifier is reserved.
Updated: Feb 21, 2026
Technical Meaning
The ERROR_DS_RESERVED_MAPI_ID error indicates that a schema update operation failed because the MAPI identifier being used is reserved. This error typically occurs in scenarios where an attempt is made to modify or define a new attribute or object type within the directory service, and the identifier chosen for this purpose conflicts with predefined or reserved identifiers.
Error Details
The ERROR_DS_RESERVED_MAPI_ID error code is returned when a schema update operation encounters a conflict with a reserved MAPI identifier. This can happen in various contexts where the directory service interacts with MAPI (Messaging Application Programming Interface) components, such as during the definition of new attributes or object types.
Usage Context
This error is relevant to developers working on applications that interact with Active Directory schema or other directory services through MAPI interfaces. It may also be encountered in scenarios where custom schema modifications are attempted, particularly when using tools or APIs that manage directory service schemas.
Developer Interpretation
When encountering the ERROR_DS_RESERVED_MAPI_ID error, developers should ensure that any identifiers used for attributes or object types do not conflict with reserved MAPI identifiers. This includes verifying that all custom schema definitions adhere to the naming conventions and guidelines provided by Microsoft for MAPI identifiers.
Related Errors
- ERROR_DS_ATTRIBUTE_OR_VALUE_EXISTS: Indicates an attempt to add a duplicate attribute or value.
- ERROR_DS_DRA_SCHEMA_CONFLICT: Occurs when there is a conflict between the local schema and the remote schema during replication.
- ERROR_DS_OBJECT_CLASS_VIOLATION: Indicates that an object does not match its class definition.
FAQ
Q: What causes ERROR_DS_RESERVED_MAPI_ID?
A: This error occurs when a reserved MAPI identifier is used in a schema update operation. Ensure all identifiers are unique and do not conflict with predefined or reserved values.
Q: How can I resolve this issue?
A: Review the identifiers being used in your schema definitions and ensure they comply with Microsoft's naming conventions for MAPI identifiers. Correct any conflicts before retrying the schema update.
Summary
The ERROR_DS_RESERVED_MAPI_ID error signifies a conflict between an identifier used in a schema update operation and reserved MAPI identifiers. Developers should carefully manage attribute and object type definitions to avoid such conflicts, ensuring compliance with Microsoft's guidelines for MAPI identifiers.