# MTA-STS DNS TXT Record Lookup

> MTA-STS DNS TXT Record Lookup is a paid API for AI agents from agentshelf.syntexa.ch, paid per call via x402, $0.004/call, status unknown (last checked 2026-10-23).

Retrieves the MTA-STS DNS TXT record (starting with v=STSv1) for a given hostname

## Facts

- Endpoint: POST https://agentshelf.syntexa.ch/v1/dns-txt-mta-sts?utm_source=zero.xyz
- Price: $0.004/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-23
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/mta-sts-dns-txt-record-lookup-a473c95c
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_lDujC5lfFwjNlT6WVyiqh

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 mta-sts-dns-txt-record-lookup-a473c95c -d '<json body>'
```

Example prompt: Can you look up the MTA-STS DNS TXT record for gmail.com and tell me if it starts with v=STSv1?

## When to prefer this

Use this endpoint when you need to programmatically retrieve and inspect the MTA-STS DNS TXT record for a hostname, particularly to verify email transport security policy configuration. Prefer the sandbox endpoint (/v1/sandbox/dns-txt-mta-sts) for testing without incurring the $0.004 USDC cost.

## Known failure modes

- Hostname not found or does not exist — DNS resolution failure
- No _mta-sts TXT record present for the domain — empty or null result
- Malformed hostname input exceeding 253 characters — validation error
- Domain has TXT record but not starting with v=STSv1 — returned as-is
- Network timeout when querying DNS
- Payment failure if x402 USDC payment not completed

## How this service works

Call when an agent needs TXT at _mta-sts that starts with v=STSv1. Exact $0.004 USDC. Prefer unpaid POST /v1/sandbox/dns-txt-mta-sts first.

## Output

Returns the content of the _mta-sts DNS TXT record for the specified hostname, expected to begin with 'v=STSv1', indicating the domain's MTA-STS policy version and any associated policy identifiers.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "hostname": {
   "type": "string",
   "examples": [
    "example.com"
   ],
   "maxLength": 253,
   "minLength": 1,
   "description": "Public DNS hostname such as example.com. Not a URL, not an IP literal, and not a private name."
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/mta-sts-dns-txt-record-lookup-a473c95c/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from agentshelf.syntexa.ch](https://www.zero.xyz/host/agentshelf.syntexa.ch/llms.txt)