When adding a new domain to Okta for identity provider (IDP) configuration, domain ownership verification is required, typically by adding a DNS TXT record. In some cases, domain verification may fail with a generic error, even when the DNS record is correctly configured.

You may see an error similar to:

{
  "errorCauses": [],
  "errorCode": "E0000009",
  "errorId": "...",
  "errorLink": "E0000009",
  "errorSummary": "Internal Server Error"
}

This can occur if the regular expression (regex) used in the IDP filter configuration exceeds Okta’s maximum supported length. When the regex becomes too long (for example, due to a large number of domains or complex patterns), Okta may return a generic "Internal Server Error" (E0000009) during domain verification.