# SMTP Envelope Transaction Command Sequencing Validator

> SMTP Envelope Transaction Command Sequencing Validator is a paid API for AI agents from detect.halowerk.com, paid per call via x402, $0.003/call, status unknown (last checked 2026-11-04).

Validates whether a normalized SMTP command ledger respects envelope sequencing rules and correctly resets transaction state after a rejected end-of-DATA command.

## Facts

- Endpoint: POST https://detect.halowerk.com/v1/F-A-NIGHT-PROTOCOL-SMTP/smtp-envelope-transaction-command-sequencing?utm_source=zero.xyz
- Price: $0.003/call
- Payment: x402
- Status: unknown
- Last checked: 2026-11-04
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/smtp-envelope-transaction-command-sequencing-validator-5156cb59
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_jA1-VBja08pHpsqr8oDvO

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability smtp-envelope-transaction-command-sequencing-validator-5156cb59 -d '<json body>'
```

Example prompt: Check whether this SMTP command ledger respects envelope sequencing and confirm that after a rejected end-of-DATA the transaction resets correctly before the next MAIL — here are the events: [{"op":"EHLO","outcome":"250"},{"op":"MAIL FROM","outcome":"250"},{"op":"RCPT TO","outcome":"250"},{"op":"DATA","outcome":"554"},{"op":"MAIL FROM","outcome":"250"}] with a claim value of 1.

## When to prefer this

Use this endpoint when you need offline, side-effect-free SMTP protocol conformance testing — specifically to verify envelope command ordering and post-rejection transaction reset behavior without sending any mail or touching real SMTP infrastructure. Prefer this over live SMTP testing tools when privacy, reproducibility, or no-send guarantees are required.

## Known failure modes

- Malformed smtp_envelope object missing required claim or events fields returns a 400 validation error
- Events array exceeding 512 items is rejected
- Individual op or outcome strings exceeding 1024 characters are rejected
- Claim value outside the range -1000000000000 to 1000000000000 is rejected
- Empty events array may produce inconclusive sequencing result

## How this service works

An offline SMTP client test agent needs whether a normalized command ledger respects envelope sequencing and whether a rejected end-of-DATA still resets the transaction before the next MAIL, without sending mail or exposing contacts.

## Output

Returns a conformance verdict indicating whether the supplied SMTP command event sequence respects envelope sequencing rules, whether a rejected end-of-DATA correctly triggers a transaction reset, and a check against the supplied claim value — all without sending actual email or exposing any contact information.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "artifact": {
   "type": "object",
   "required": [
    "smtp_envelope"
   ],
   "properties": {
    "smtp_envelope": {
     "type": "object",
     "required": [
      "claim",
      "events"
     ],
     "properties": {
      "claim": {
       "type": "number",
       "maximum": 1000000000000,
       "minimum": -1000000000000
      },
      "events": {
       "type": "array",
       "items": {
        "type": "object",
        "required": [
         "op",
         "outcome"
        ],
        "properties": {
         "op": {
          "type": "string",
          "maxLength": 1024
         },
         "outcome": {
          "type": "string",
          "maxLength": 1024
         }
        },
        "additionalProperties": false
       },
       "maxItems": 512
      }
     },
     "additionalProperties": false
    }
   },
   "additionalProperties": false
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/smtp-envelope-transaction-command-sequencing-validator-5156cb59/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from detect.halowerk.com](https://www.zero.xyz/host/detect.halowerk.com/llms.txt)