Exact response pattern
534 5.7.9 Application-specific password requiredPermanentGenericAuthentication
What it means
The mailbox provider requires an app password or modern authentication policy.
Likely causes
- Multi-factor authentication enabled.
- Basic password rejected.
Recommended response
- Create an app password where supported.
- Prefer OAuth or the provider-supported authentication method.
Operational rule: Preserve the complete SMTP response, remote hostname, sending IP, envelope sender and timestamp. Never diagnose from the three-digit code alone.