Problem Definition

The Confluence Data Center REST API endpoint POST /rest/api/admin/user (used to create users in the internal directory) performs a stricter email validation than the Confluence UI in versions prior to 10.0. Specifically, the API returns a HTTP 400 Bad Request with the error "Invalid email address" if the email domain uses a Top-Level Domain (TLD) not registered in the IANA Root Zone Database.

This causes confusion for customers using private or custom TLDs (e.g., .local, .xix, or internal-only domains) because:

1. The user can be created successfully via the Confluence UI (in versions 8.x and 9.x).

1. The error message "Invalid email address" is generic and does not specify that the TLD is the cause of the failure.

1. There is no mention in the The Confluence Data Center REST API that the library (Apache Commons Validator) strictly enforces IANA-registered TLDs.

Suggested Solution

1. Documentation Update: Update the REST API documentation for POST /rest/api/admin/user to explicitly state that email addresses are validated against the IANA Root Zone Database.

1. KB Article: Publish a Knowledge Base article explaining the discrepancy between UI and API validation paths in Confluence 8.x/9.x and the alignment of these paths in Confluence 10.0+.