{
  "id": "communication/smtp-535-authentication-credentials-invalid",
  "signature": "535 5.7.8 Authentication credentials invalid: SMTP server rejected username/password",
  "signature_zh": "535 5.7.8 身份验证凭据无效：SMTP 服务器拒绝用户名/密码",
  "regex": "535\\s+5\\.7\\.8\\s+Authentication credentials invalid",
  "domain": "communication",
  "category": "auth_error",
  "subcategory": null,
  "root_cause": "SMTP authentication failed because the provided username or password does not match the server's authentication backend, often due to app-specific password requirements or OAuth token expiration.",
  "root_cause_type": "generic",
  "root_cause_zh": "SMTP 身份验证失败，因为提供的用户名或密码与服务器的身份验证后端不匹配，通常是由于应用专用密码要求或 OAuth 令牌过期。",
  "versions": [
    {
      "version": "Postfix 3.7",
      "introduced": null,
      "deprecated": null,
      "removed": null,
      "behavior_change": null,
      "status": "active"
    },
    {
      "version": "Exim 4.96",
      "introduced": null,
      "deprecated": null,
      "removed": null,
      "behavior_change": null,
      "status": "active"
    },
    {
      "version": "Microsoft Exchange 2019",
      "introduced": null,
      "deprecated": null,
      "removed": null,
      "behavior_change": null,
      "status": "active"
    },
    {
      "version": "SendGrid SMTP relay",
      "introduced": null,
      "deprecated": null,
      "removed": null,
      "behavior_change": null,
      "status": "active"
    }
  ],
  "os_specific": {},
  "dead_ends": [
    {
      "action": "Re-enter the same credentials in the SMTP client configuration",
      "why_fails": "If credentials are invalid or expired, re-entering them does not resolve the underlying issue (e.g., app password required).",
      "fail_rate": 0.7,
      "condition": "",
      "sources": []
    },
    {
      "action": "Disable SMTP authentication entirely in client settings",
      "why_fails": "Most SMTP servers require authentication for relay; disabling it may cause 'Relay access denied' errors.",
      "fail_rate": 0.85,
      "condition": "",
      "sources": []
    },
    {
      "action": "Use the same password as the webmail login without generating an app-specific password",
      "why_fails": "Services like Gmail, Outlook, and Yahoo require app-specific passwords for SMTP; using the primary account password often fails.",
      "fail_rate": 0.75,
      "condition": "",
      "sources": []
    }
  ],
  "workarounds": [
    {
      "action": "Generate an app-specific password for SMTP in the email provider's security settings, e.g., Google: https://myaccount.google.com/apppasswords, then update SMTP client config with that password.",
      "success_rate": 0.95,
      "how": "Generate an app-specific password for SMTP in the email provider's security settings, e.g., Google: https://myaccount.google.com/apppasswords, then update SMTP client config with that password.",
      "condition": "",
      "sources": []
    },
    {
      "action": "Switch to OAuth 2.0 authentication for SMTP if supported, e.g., using `XOAUTH2` mechanism with a refreshed access token.",
      "success_rate": 0.85,
      "how": "Switch to OAuth 2.0 authentication for SMTP if supported, e.g., using `XOAUTH2` mechanism with a refreshed access token.",
      "condition": "",
      "sources": []
    },
    {
      "action": "Verify credentials by testing with `openssl s_client -connect smtp.example.com:587 -starttls smtp` and manually issuing `AUTH LOGIN` with base64-encoded username/password.",
      "success_rate": 0.9,
      "how": "Verify credentials by testing with `openssl s_client -connect smtp.example.com:587 -starttls smtp` and manually issuing `AUTH LOGIN` with base64-encoded username/password.",
      "condition": "",
      "sources": []
    }
  ],
  "workarounds_zh": [
    "在邮件提供商的安全设置中生成应用专用密码，例如 Google：https://myaccount.google.com/apppasswords，然后用该密码更新 SMTP 客户端配置。",
    "如果支持，切换到 OAuth 2.0 身份验证用于 SMTP，例如使用 `XOAUTH2` 机制并配合刷新的访问令牌。",
    "通过 `openssl s_client -connect smtp.example.com:587 -starttls smtp` 测试凭据，手动使用 base64 编码的用户名/密码执行 `AUTH LOGIN`。"
  ],
  "transition_graph": {
    "leads_to": [],
    "preceded_by": [],
    "frequently_confused_with": []
  },
  "official_doc_url": "https://datatracker.ietf.org/doc/html/rfc4954",
  "official_doc_section": null,
  "error_code": "535",
  "verification_tier": "ai_generated",
  "confidence": 0.88,
  "fix_success_rate": 0.9,
  "resolvable": "true",
  "first_seen": "2023-06-20",
  "last_confirmed": "2024-06-01",
  "last_updated": "2024-06-01",
  "evidence_count": 1,
  "tags": [],
  "locale": "en",
  "aliases": []
}