{
  "id": "communication/smtp-rate-limit-exceeded",
  "signature": "450 4.7.1 Requested action not taken: rate limit exceeded",
  "signature_zh": "450 4.7.1 请求的操作未执行：超出速率限制",
  "regex": "450 4\\.7\\.1 Requested action not taken: rate limit exceeded",
  "domain": "communication",
  "category": "runtime_error",
  "subcategory": null,
  "root_cause": "The SMTP server has a per-connection or per-sender rate limit that has been exceeded, often due to sending too many emails in a short period.",
  "root_cause_type": "generic",
  "root_cause_zh": "SMTP 服务器每连接或每发件人的速率限制已超出，通常由于短时间内发送过多邮件。",
  "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": "Sendmail 8.17",
      "introduced": null,
      "deprecated": null,
      "removed": null,
      "behavior_change": null,
      "status": "active"
    }
  ],
  "os_specific": {},
  "dead_ends": [
    {
      "action": "",
      "why_fails": "Increasing connection pool size without throttling may hit per-sender limit faster.",
      "fail_rate": 0.7,
      "condition": "",
      "sources": []
    },
    {
      "action": "",
      "why_fails": "Switching to a different SMTP port (e.g., 587 vs 465) doesn't bypass rate limits.",
      "fail_rate": 0.9,
      "condition": "",
      "sources": []
    },
    {
      "action": "",
      "why_fails": "Adding more sender addresses without reducing per-address rate still triggers limits on each.",
      "fail_rate": 0.6,
      "condition": "",
      "sources": []
    }
  ],
  "workarounds": [
    {
      "action": "Implement exponential backoff with jitter: wait 2^retry seconds + random(0-1s) before retrying. Example in Python: `time.sleep(min(2**attempt + random.uniform(0, 1), 60))`.",
      "success_rate": 0.82,
      "how": "Implement exponential backoff with jitter: wait 2^retry seconds + random(0-1s) before retrying. Example in Python: `time.sleep(min(2**attempt + random.uniform(0, 1), 60))`.",
      "condition": "",
      "sources": []
    },
    {
      "action": "Throttle sending rate to N emails per second per connection (e.g., 10 emails/s) using a token bucket algorithm.",
      "success_rate": 0.78,
      "how": "Throttle sending rate to N emails per second per connection (e.g., 10 emails/s) using a token bucket algorithm.",
      "condition": "",
      "sources": []
    }
  ],
  "workarounds_zh": [
    "Implement exponential backoff with jitter: wait 2^retry seconds + random(0-1s) before retrying. Example in Python: `time.sleep(min(2**attempt + random.uniform(0, 1), 60))`.",
    "Throttle sending rate to N emails per second per connection (e.g., 10 emails/s) using a token bucket algorithm."
  ],
  "transition_graph": {
    "leads_to": [],
    "preceded_by": [],
    "frequently_confused_with": []
  },
  "official_doc_url": "https://tools.ietf.org/html/rfc5321#section-4.2.5",
  "official_doc_section": null,
  "error_code": "450 4.7.1",
  "verification_tier": "ai_generated",
  "confidence": 0.84,
  "fix_success_rate": 0.82,
  "resolvable": "true",
  "first_seen": "2023-07-01",
  "last_confirmed": "2024-06-01",
  "last_updated": "2024-06-01",
  "evidence_count": 1,
  "tags": [
    "SMTP",
    "rate-limit",
    "email"
  ],
  "locale": "en",
  "aliases": []
}