●

StableEmail

AI PAYMENT-READY

payment-ready until 2026-09-10

Pay-per-send email via micropayments. AWS SES backend. Supports subdomains, inboxes, and replies. USDC on Base or Solana.

Pay from $0.02 to $5.00 in USDC on Base / Solana, settled onchain via the x402 protocol, no signup, no API key needed.

BASE URL https://stableemail.dev │ ENDPOINTS 3 │ NETWORK Base / Solana │ ASSET USDC │ MEMBER SINCE 2026-02-05 │ MONITORED SINCE 2026-04-15

VERDICT

ranking generation 3

strong 93/100 #18 of 104 in AI by measured score

What the score read on this service: status online, 100% uptime 30d, 869ms response p95, x402 compliance 14 of 14, $0.02 price against the category. Each of those is measured, and each is published in full below.

The score comes from our own monitoring, never from reviews, operator claims, or a language model: reliability, x402 compliance, price against the category, a deterministic risk flag, and a small on-chain traction term, weighted by ranking generation 3. It is not placement anyone can buy: the paid verify tier is reported beside it and is not one of its inputs. Every component below stays published and read-only.

It is a score inside AI, and only there: price and speed are scored against the whole category field, every listing in it that carries no danger flag, the scored service included, which here means 104 listings, this one among them. That set is wider than the 104 the position above is counted against, because a listing we have measured too little of to rank still sits in the field the price and the speed are normalized over. The same service in a different field would read differently. The same engine answers GET /api/v1/best, and asked for a different pool (the whole directory, or another filter) it returns a different number for this service under this same ranking generation. Neither is more correct: they answer different questions, and the methodology states which is which.

Bands on the 0 to 100 measured score: strong at 93 and above, solid from 75, mixed from 55, weak below 55. Price and speed are scored against the whole category field, every listing in it that carries no danger flag, the scored service included, so the score places a service in its own field.

ALTERNATIVES IN AI

Other AI services in this directory, ordered by the same measured score. The figures are ours: 30-day uptime from our own probes, 30-day settlement volume read on-chain (a conservative undercount, and null where we cannot measure it, never a zero).

Ranked alternative x402 services in the same category, with band, measured score, 30-day uptime and 30-day on-chain settlement volume
SERVICE	BAND	SCORE	UPTIME 30D	VOL 30D
Otto AI	strong	99	100%	---
Japan Furigana API	strong	97	99.1%	---
BridgeNode	strong	97	99.3%	---
Spraay Gateway	strong	96	100%	---
Agent402.tools	strong	96	98.5%	---

5 of 103 other ranked services in AI · see the whole category

ASSESSMENT

updated 36m ago

The parts the verdict above is computed from, each with its proof. Click any chip. Measured values stay read-only; unknown is honest, and an unknown is never counted as a zero.

reliability 100%

uptime 24h: 100%
uptime 7d: 100%
uptime 30d: 100%
uptime 90d: 100%
response p95: 869ms
avg response: 325ms
total checks: 7,368

Measured on the unpaid 402 handshake, not the paid call. A service can 402 correctly and still fail after payment.

compliance A (14/14)

14 of 14 x402 conformance checks pass. Full checklist below.

jump to compliance checklist

price $0.02 to $5.00 (p60 in AI)

price (min): $0.02
price (max): $5.00
category percentile (min): p60 in AI
category percentile (max): p86 in AI
endpoints / prices: 3 / 3
model: tiered
stability: 100%

risk clean

No deterministic risk flag. Risk fires only on an exact blocklist match, or a reserved-brand name with a mismatched verified payTo. Never from low uptime, a high price, or a model guess.

domain age: -
registrar: -
hosting: custom
domain created: ---

Identity facts, not a risk score.

traction ---

This service settles on a network x402-list does not measure yet, so on-chain volume is not counted here. Shown as unmeasured, not zero.

CHANGES

1 in 30d

Payout, price, and schema changes detected on this service's x402 wire. A payout rotation at an unchanged price shows up here even when nothing else moves. Full feed at /changes.

changes schema changed 14d ago (1 in 30d)

schema changed · 14d ago

schema removed POST /api/inbox/buy exact solana:5eykt4usfv8p8njdtrepy1vzqkqzkvdp EPjFWdd5AufqSSqeM2qN1xzybapC8G4wEGGkZwyTDt1v USDC 2 300 {"feePayer":"2wKupLR9q6wXYppw8Gr2NvWxKBUqm4PPJKkQfoxHDBg4"}

schema removed POST /api/send exact solana:5eykt4usfv8p8njdtrepy1vzqkqzkvdp EPjFWdd5AufqSSqeM2qN1xzybapC8G4wEGGkZwyTDt1v USDC 2 300 {"feePayer":"2wKupLR9q6wXYppw8Gr2NvWxKBUqm4PPJKkQfoxHDBg4"}

schema removed POST /api/subdomain/buy exact solana:5eykt4usfv8p8njdtrepy1vzqkqzkvdp EPjFWdd5AufqSSqeM2qN1xzybapC8G4wEGGkZwyTDt1v USDC 2 300 {"feePayer":"2wKupLR9q6wXYppw8Gr2NvWxKBUqm4PPJKkQfoxHDBg4"}

schema added POST /api/inbox/buy exact solana:5eykt4usfv8p8njdtrepy1vzqkqzkvdp EPjFWdd5AufqSSqeM2qN1xzybapC8G4wEGGkZwyTDt1v USDC 2 300 {"feePayer":"CjNFTjvBhbJJd2B5ePPMHRLx1ELZpa8dwQgGL727eKww"}

schema added POST /api/send exact solana:5eykt4usfv8p8njdtrepy1vzqkqzkvdp EPjFWdd5AufqSSqeM2qN1xzybapC8G4wEGGkZwyTDt1v USDC 2 300 {"feePayer":"CjNFTjvBhbJJd2B5ePPMHRLx1ELZpa8dwQgGL727eKww"}

schema added POST /api/subdomain/buy exact solana:5eykt4usfv8p8njdtrepy1vzqkqzkvdp EPjFWdd5AufqSSqeM2qN1xzybapC8G4wEGGkZwyTDt1v USDC 2 300 {"feePayer":"CjNFTjvBhbJJd2B5ePPMHRLx1ELZpa8dwQgGL727eKww"}

see all changes for this service

WHAT IT DOES

ai-derived

No AI synthesis has been produced for this service yet.

ENDPOINTS

Service endpoints with HTTP method, path, description, pricing, and network
METHOD	PATH	DESCRIPTION	PRICE	NETWORK	ASSET	402 CHANNEL
POST	/api/inbox/buy	Buy a managed inbox	$1.00	Base/Solana	USDC	header
POST	/api/send	Send email	$0.02	Base/Solana	USDC	header
POST	/api/subdomain/buy	Buy a subdomain	$5.00	Base/Solana	USDC	header

3 endpoints

REQUEST / RESPONSE EXAMPLE

An unpaid request to POST /api/inbox/buy returns HTTP 402 with the payment terms. Settle onchain via your facilitator, then retry with the X-Payment header.

// request

curl -i -X POST 'https://stableemail.dev/api/inbox/buy'

// 402 response (captured by monitor) · 3 payloads · click to expand

[
  {
    "accepts": [
      {
        "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
        "extra": {
          "name": "USD Coin",
          "version": "2"
        },
        "payTo": "0xdb5aa553feeb2c3e3d03e8360b36fb0f7e480671",
        "amount": "5000000",
        "scheme": "exact",
        "network": "eip155:8453",
        "maxTimeoutSeconds": 300
      },
      {
        "asset": "EPjFWdd5AufqSSqeM2qN1xzybapC8G4wEGGkZwyTDt1v",
        "extra": {
          "feePayer": "CjNFTjvBhbJJd2B5ePPMHRLx1ELZpa8dwQgGL727eKww"
        },
        "payTo": "HvBMG7ezcwDssxXP7DPJJsveyDnvUm2wNySBR5WF2XEY",
        "amount": "5000000",
        "scheme": "exact",
        "network": "solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp",
        "maxTimeoutSeconds": 300
      }
    ],
    "resource": {
      "url": "https://stableemail.dev/api/subdomain/buy",
      "tags": [
        "Subdomain"
      ],
      "method": "POST",
      "mimeType": "application/json",
      "description": "Purchase a custom email subdomain on stableemail.dev ($5)",
      "serviceName": "StableEmail"
    },
    "extensions": {
      "bazaar": {
        "info": {
          "input": {
            "body": {
              "subdomain": "my-brand"
            },
            "type": "http",
            "method": "POST",
            "bodyType": "json"
          }
        },
        "schema": {
          "type": "object",
          "$schema": "https://json-schema.org/draft/2020-12/schema",
          "required": [
            "input"
          ],
          "properties": {
            "input": {
              "type": "object",
              "required": [
                "type",
                "method",
                "bodyType",
                "body"
              ],
              "properties": {
                "body": {
                  "type": "object",
                  "$schema": "https://json-schema.org/draft/2020-12/schema",
                  "required": [
                    "subdomain"
                  ],
                  "properties": {
                    "subdomain": {
                      "type": "string",
                      "allOf": [
                        {
                          "pattern": "^[a-z0-9][a-z0-9-]{1,28}[a-z0-9]$"
                        },
                        {
                          "pattern": "^(?!.*--)"
                        }
                      ]
                    }
                  },
                  "additionalProperties": false
                },
                "type": {
                  "type": "string",
                  "const": "http"
                },
                "method": {
                  "enum": [
                    "POST",
                    "PUT",
                    "PATCH"
                  ],
                  "type": "string"
                },
                "bodyType": {
                  "enum": [
                    "json",
                    "form-data",
                    "text"
                  ],
                  "type": "string"
                }
              },
              "additionalProperties": false
            }
          }
        }
      }
    },
    "x402Version": 2
  },
  {
    "accepts": [
      {
        "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
        "extra": {
          "name": "USD Coin",
          "version": "2"
        },
        "payTo": "0xdb5aa553feeb2c3e3d03e8360b36fb0f7e480671",
        "amount": "1000000",
        "scheme": "exact",
        "network": "eip155:8453",
        "maxTimeoutSeconds": 300
      },
      {
        "asset": "EPjFWdd5AufqSSqeM2qN1xzybapC8G4wEGGkZwyTDt1v",
        "extra": {
          "feePayer": "CjNFTjvBhbJJd2B5ePPMHRLx1ELZpa8dwQgGL727eKww"
        },
        "payTo": "HvBMG7ezcwDssxXP7DPJJsveyDnvUm2wNySBR5WF2XEY",
        "amount": "1000000",
        "scheme": "exact",
        "network": "solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp",
        "maxTimeoutSeconds": 300
      }
    ],
    "resource": {
      "url": "https://stableemail.dev/api/inbox/buy",
      "tags": [
        "Inbox"
      ],
      "method": "POST",
      "mimeType": "application/json",
      "description": "Buy an inbox on stableemail.dev ($1, 30 days). forwardTo is optional — omit it to use as a programmatic mailbox via the messages API (retainMessages enabled automatically). Message content and attachments are retained for 90 days.",
      "serviceName": "StableEmail"
    },
    "extensions": {
      "bazaar": {
        "info": {
          "input": {
            "body": {
              "username": "my-inbox"
            },
            "type": "http",
            "method": "POST",
            "bodyType": "json"
          }
        },
        "schema": {
          "type": "object",
          "$schema": "https://json-schema.org/draft/2020-12/schema",
          "required": [
            "input"
          ],
          "properties": {
            "input": {
              "type": "object",
              "required": [
                "type",
                "method",
                "bodyType",
                "body"
              ],
              "properties": {
                "body": {
                  "type": "object",
                  "$schema": "https://json-schema.org/draft/2020-12/schema",
                  "required": [
                    "username"
                  ],
                  "properties": {
                    "username": {
                      "type": "string",
                      "allOf": [
                        {
                          "pattern": "^[a-z0-9][a-z0-9-]{1,28}[a-z0-9]$"
                        },
                        {
                          "pattern": "^(?!.*--)"
                        }
                      ]
                    },
                    "forwardTo": {
                      "type": "string",
                      "format": "email",
                      "pattern": "^(?!\\.)(?!.*\\.\\.)([A-Za-z0-9_'+\\-\\.]*)[A-Za-z0-9_+-]@([A-Za-z0-9][A-Za-z0-9\\-]*\\.)+[A-Za-z]{2,}$"
                    }
                  },
                  "additionalProperties": false
                },
                "type": {
                  "type": "string",
                  "const": "http"
                },
                "method": {
                  "enum": [
                    "POST",
                    "PUT",
                    "PATCH"
                  ],
                  "type": "string"
                },
                "bodyType": {
                  "enum": [
                    "json",
                    "form-data",
                    "text"
                  ],
                  "type": "string"
                }
              },
              "additionalProperties": false
            }
          }
        }
      }
    },
    "x402Version": 2
  },
  {
    "accepts": [
      {
        "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
        "extra": {
          "name": "USD Coin",
          "version": "2"
        },
        "payTo": "0xdb5aa553feeb2c3e3d03e8360b36fb0f7e480671",
        "amount": "20000",
        "scheme": "exact",
        "network": "eip155:8453",
        "maxTimeoutSeconds": 300
      },
      {
        "asset": "EPjFWdd5AufqSSqeM2qN1xzybapC8G4wEGGkZwyTDt1v",
        "extra": {
          "feePayer": "CjNFTjvBhbJJd2B5ePPMHRLx1ELZpa8dwQgGL727eKww"
        },
        "payTo": "HvBMG7ezcwDssxXP7DPJJsveyDnvUm2wNySBR5WF2XEY",
        "amount": "20000",
        "scheme": "exact",
        "network": "solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp",
        "maxTimeoutSeconds": 300
      }
    ],
    "resource": {
      "url": "https://stableemail.dev/api/send",
      "tags": [
        "Send"
      ],
      "method": "POST",
      "mimeType": "application/json",
      "description": "Send an email from \"StableEmail\" <[email protected]> ($0.02)",
      "serviceName": "StableEmail"
    },
    "extensions": {
      "bazaar": {
        "info": {
          "input": {
            "body": {},
            "type": "http",
            "method": "POST",
            "bodyType": "json"
          }
        },
        "schema": {
          "type": "object",
          "$schema": "https://json-schema.org/draft/2020-12/schema",
          "required": [
            "input"
          ],
          "properties": {
            "input": {
              "type": "object",
              "required": [
                "type",
                "method",
                "bodyType",
                "body"
              ],
              "properties": {
                "body": {
                  "type": "object",
                  "$schema": "https://json-schema.org/draft/2020-12/schema",
                  "required": [
                    "to",
                    "subject"
                  ],
                  "properties": {
                    "cc": {
                      "type": "array",
                      "items": {
                        "type": "string",
                        "format": "email",
                        "pattern": "^(?!\\.)(?!.*\\.\\.)([A-Za-z0-9_'+\\-\\.]*)[A-Za-z0-9_+-]@([A-Za-z0-9][A-Za-z0-9\\-]*\\.)+[A-Za-z]{2,}$"
                      },
                      "maxItems": 50,
                      "minItems": 1
                    },
                    "to": {
                      "type": "array",
                      "items": {
                        "type": "string",
                        "format": "email",
                        "pattern": "^(?!\\.)(?!.*\\.\\.)([A-Za-z0-9_'+\\-\\.]*)[A-Za-z0-9_+-]@([A-Za-z0-9][A-Za-z0-9\\-]*\\.)+[A-Za-z]{2,}$"
                      },
                      "maxItems": 50,
                      "minItems": 1
                    },
                    "html": {
                      "type": "string",
                      "maxLength": 256000
                    },
                    "text": {
                      "type": "string",
                      "maxLength": 256000
                    },
                    "replyTo": {
                      "type": "string",
                      "format": "email",
                      "pattern": "^(?!\\.)(?!.*\\.\\.)([A-Za-z0-9_'+\\-\\.]*)[A-Za-z0-9_+-]@([A-Za-z0-9][A-Za-z0-9\\-]*\\.)+[A-Za-z]{2,}$"
                    },
                    "subject": {
                      "type": "string",
                      "maxLength": 998,
                      "minLength": 1
                    },
                    "attachments": {
                      "type": "array",
                      "items": {
                        "type": "object",
                        "required": [
                          "content",
                          "contentType",
                          "filename"
                        ],
                        "properties": {
                          "content": {
                            "type": "string",
                            "maxLength": 5000000
                          },
                          "filename": {
                            "type": "string",
                            "maxLength": 255,
                            "minLength": 1
                          },
                          "contentType": {
                            "type": "string",
                            "maxLength": 255,
                            "minLength": 1
                          }
                        },
                        "additionalProperties": false
                      },
                      "maxItems": 5
                    }
                  },
                  "additionalProperties": false
                },
                "type": {
                  "type": "string",
                  "const": "http"
                },
                "method": {
                  "enum": [
                    "POST",
                    "PUT",
                    "PATCH"
                  ],
                  "type": "string"
                },
                "bodyType": {
                  "enum": [
                    "json",
                    "form-data",
                    "text"
                  ],
                  "type": "string"
                }
              },
              "additionalProperties": false
            }
          }
        }
      }
    },
    "x402Version": 2
  }
]

OVER TIME

All charts use the 30d selector; each series spans only the dates it has data for. Every series is also served as JSON at /api/v1/services/stableemail/price, /scores, /volume and /buyers. On-chain volume and distinct buyers are measured over the service's settlement address and are a conservative undercount (only settlements that reach a measured facilitator are counted). The on-chain series roll up hourly, so the latest day can be up to about an hour behind; distinct buyers are counted per payout address, so a service that settles to more than one address is an upper bound.

UPTIME

30d UPTIME 100%

RESPONSE TIME

AVG RESP 325ms

PRICE (captured 402, USD)

Median across 3 endpoints. Use the selector to isolate one.

SUB-SCORES (uptime + x402 compliance)

checklist grew 11->14 on 2026-07-28; a step here is a metric change, not a regression

PILLARS OVER TIME (measured)

price percentile in AI

site signals present (of 6)

Measured site and economics pillars from the assessment history, so the latest value shown elsewhere on this page reads as a point on a trend rather than a permanent state.

VOLUME (on-chain settlement, USD)

This service settles on a network x402-list does not measure yet, so on-chain volume is not counted here. Shown as unmeasured, not zero.

DISTINCT BUYERS

This service settles on a network x402-list does not measure yet, so distinct on-chain buyers are not counted here. Shown as unmeasured, not zero.

COMPLIANCE

14/14 checks pass · grade A

last 402 captured 2026-08-20 · last up 2026-09-03

402 payload captured
accepts[] array present
payTo address recoverable
payTo at accepts[0].payTo (conformant shape)
payTo is a valid on-chain address
atomic price declared
atomic price in a sane range
asset (token) address declared
network resolves to CAIP-2
payment scheme declared
served over HTTPS
declares the current x402 version (2)
EIP-712 domain parameters present on every EVM entry
x402 v2 envelope delivered in the payment-required header

SITE PILLARS

homepage reachable
openapi doc
pricing page
llms.txt
robots.txt
terms page

recent checks (18) live · click to expand

TIME STATUS RESP CAUSE

20:53:01 UTC ● OK 468ms

20:47:01 UTC ● OK 421ms

20:41:01 UTC ● OK 450ms

20:35:01 UTC ● SLOW 568ms

20:29:00 UTC ● OK 126ms

20:23:00 UTC ● OK 209ms

20:17:00 UTC ● OK 92ms

20:11:01 UTC ● OK 415ms

20:05:01 UTC ● OK 329ms

19:59:01 UTC ● SLOW 605ms

19:53:02 UTC ● SLOW 944ms

19:47:01 UTC ● OK 359ms

19:41:01 UTC ● OK 449ms

19:35:01 UTC ● SLOW 496ms

19:28:01 UTC ● OK 338ms

19:22:01 UTC ● SLOW 498ms

19:16:02 UTC ● SLOW 792ms

19:10:02 UTC ● OK 272ms

EMBED THIS BADGE

Show that StableEmail is monitored on x402-list. Paste this on your site or README, it links back to this live listing.

status

StableEmail uptime on x402-list — live uptime

// HTML

<a href="https://x402-list.com/services/stableemail?utm_source=badge&utm_medium=referral&utm_campaign=embed">
  <img src="https://x402-list.com/badge/stableemail.svg" alt="StableEmail listed on x402-list" height="28">
</a>

// Markdown

[![StableEmail on x402-list](https://x402-list.com/badge/stableemail.svg)](https://x402-list.com/services/stableemail?utm_source=badge&utm_medium=referral&utm_campaign=embed)

// HTML · live uptime variant

<a href="https://x402-list.com/services/stableemail?utm_source=badge&utm_medium=referral&utm_campaign=embed">
  <img src="https://x402-list.com/badge/stableemail.svg?data=uptime" alt="StableEmail uptime on x402-list" height="28">
</a>

RUN THIS SERVICE?

Keep this listing accurate: propose changes to the name, description, website, category or add new endpoints to monitor. Ownership is verified with a domain proof and every change is reviewed manually; measured data stays read-only.

[ update this listing ]

Earn the verified tier: x402list pays a real call to this endpoint and, if it delivers, the service is delivery-verified. The fee covers the cost of the probe, not the badge; there is no refund if the call does not deliver. Agent and API only, no in-browser signing. See /api.

[ verify this service ($0.25) ]

To request delisting, email info@x402-list.com or update your listing at /services/stableemail/update.