{
  "id": "communication/smtp-550-spamhaus-blocked",
  "signature": "550 5.7.1 Service unavailable; Client host [x.x.x.x] blocked using Spamhaus",
  "signature_zh": "550 5.7.1 服务不可用；客户端主机 [x.x.x.x] 被 Spamhaus 阻止",
  "regex": "550.*Spamhaus",
  "domain": "communication",
  "category": "auth_error",
  "subcategory": null,
  "root_cause": "The sending IP address is listed in the Spamhaus Block List (SBL) or Exploits Block List (XBL), causing the receiving MTA to reject the connection as spam.",
  "root_cause_type": "generic",
  "root_cause_zh": "发送 IP 地址被列入 Spamhaus 阻止列表（SBL）或漏洞利用阻止列表（XBL），导致接收 MTA 拒绝连接，视为垃圾邮件。",
  "versions": [
    {
      "version": "Postfix 3.8",
      "introduced": null,
      "deprecated": null,
      "removed": null,
      "behavior_change": null,
      "status": "active"
    },
    {
      "version": "Sendmail 8.17",
      "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": "Spamhaus SBL v2",
      "introduced": null,
      "deprecated": null,
      "removed": null,
      "behavior_change": null,
      "status": "active"
    }
  ],
  "os_specific": {},
  "dead_ends": [
    {
      "action": "Change the sender email domain to a different one",
      "why_fails": "Changing the sending domain does not affect the IP reputation; the block is based on the IP address, not the domain.",
      "fail_rate": 0.92,
      "condition": "",
      "sources": []
    },
    {
      "action": "Add SPF and DKIM records to the sending domain",
      "why_fails": "Adding SPF/DKIM records does not remove the IP from the blocklist; the block is at the IP level and requires delisting.",
      "fail_rate": 0.88,
      "condition": "",
      "sources": []
    },
    {
      "action": "Restart the SMTP server (Postfix/Sendmail)",
      "why_fails": "Restarting the MTA does not change the IP's blocklist status; the IP remains listed until delisting is requested.",
      "fail_rate": 0.95,
      "condition": "",
      "sources": []
    }
  ],
  "workarounds": [
    {
      "action": "Check the IP against Spamhaus using: `dig +short x.x.x.x.zen.spamhaus.org`. If listed, visit https://www.spamhaus.org/lookup/ to request delisting after fixing the spam issue (e.g., securing the server from being an open relay).",
      "success_rate": 0.7,
      "how": "Check the IP against Spamhaus using: `dig +short x.x.x.x.zen.spamhaus.org`. If listed, visit https://www.spamhaus.org/lookup/ to request delisting after fixing the spam issue (e.g., securing the server from being an open relay).",
      "condition": "",
      "sources": []
    },
    {
      "action": "Route outgoing mail through a trusted SMTP relay or service (e.g., SendGrid, AWS SES) that has a clean IP reputation. Configure Postfix: `relayhost = [smtp.sendgrid.net]:587` with credentials.",
      "success_rate": 0.85,
      "how": "Route outgoing mail through a trusted SMTP relay or service (e.g., SendGrid, AWS SES) that has a clean IP reputation. Configure Postfix: `relayhost = [smtp.sendgrid.net]:587` with credentials.",
      "condition": "",
      "sources": []
    },
    {
      "action": "If the IP is static, contact the ISP or hosting provider to request a new IP address and update DNS records accordingly.",
      "success_rate": 0.6,
      "how": "If the IP is static, contact the ISP or hosting provider to request a new IP address and update DNS records accordingly.",
      "condition": "",
      "sources": []
    }
  ],
  "workarounds_zh": [
    "Check the IP against Spamhaus using: `dig +short x.x.x.x.zen.spamhaus.org`. If listed, visit https://www.spamhaus.org/lookup/ to request delisting after fixing the spam issue (e.g., securing the server from being an open relay).",
    "Route outgoing mail through a trusted SMTP relay or service (e.g., SendGrid, AWS SES) that has a clean IP reputation. Configure Postfix: `relayhost = [smtp.sendgrid.net]:587` with credentials.",
    "If the IP is static, contact the ISP or hosting provider to request a new IP address and update DNS records accordingly."
  ],
  "transition_graph": {
    "leads_to": [],
    "preceded_by": [],
    "frequently_confused_with": []
  },
  "official_doc_url": "https://www.spamhaus.org/faq/section/Spamhaus%20BL%20Queries",
  "official_doc_section": null,
  "error_code": "550",
  "verification_tier": "ai_generated",
  "confidence": 0.86,
  "fix_success_rate": 0.78,
  "resolvable": "partial",
  "first_seen": "2023-01-20",
  "last_confirmed": "2024-06-01",
  "last_updated": "2024-06-01",
  "evidence_count": 1,
  "tags": [],
  "locale": "en",
  "aliases": []
}