# As a condition of accessing this website, you agree to abide by the following # content signals: # (a) If a Content-Signal = yes, you may collect content for the corresponding # use. # (b) If a Content-Signal = no, you may not collect content for the # corresponding use. # (c) If the website operator does not include a Content-Signal for a # corresponding use, the website operator neither grants nor restricts # permission via Content-Signal with respect to the corresponding use. # The content signals and their meanings are: # search: building a search index and providing search results (e.g., returning # hyperlinks and short excerpts from your website's contents). Search does not # include providing AI-generated search summaries. # ai-input: inputting content into one or more AI models (e.g., retrieval # augmented generation, grounding, or other real-time taking of content for # generative AI search answers). # ai-train: training or fine-tuning AI models. # ANY RESTRICTIONS EXPRESSED VIA CONTENT SIGNALS ARE EXPRESS RESERVATIONS OF # RIGHTS UNDER ARTICLE 4 OF THE EUROPEAN UNION DIRECTIVE 2019/790 ON COPYRIGHT # AND RELATED RIGHTS IN THE DIGITAL SINGLE MARKET. # BEGIN Cloudflare Managed content User-agent: * Content-Signal: search=yes,ai-train=no Allow: / User-agent: Amazonbot Disallow: / User-agent: Applebot-Extended Disallow: / User-agent: Bytespider Disallow: / User-agent: CCBot Disallow: / User-agent: ClaudeBot Disallow: / User-agent: CloudflareBrowserRenderingCrawler Disallow: / User-agent: Google-Extended Disallow: / User-agent: GPTBot Disallow: / User-agent: meta-externalagent Disallow: / # END Cloudflare Managed Content MailerAstro — Email API for AI Agents
⭐ The first email API with x402 crypto payments

Email API for AI Agents

MailerAstro lets AI agents send emails and pay with USDC — no API keys, no accounts, no human intervention. Just pay and send.

Start Sending Free → See How It Works
For DevelopersAPI Key
# Send with API Key
curl -X POST https://api.mailerastro.com/api/v1/email/send \
  -H "X-API-Key: your_key" \
  -H "Content-Type: application/json" \
  -d '{
    "to": "user@example.com",
    "subject": "Welcome!",
    "text": "Thanks for signing up."
  }'
⭐ For AI Agentsx402
# Pay with USDC, no API key needed
curl -X POST https://api.mailerastro.com/api/v1/email/send \
  -H "X-Payer-Wallet: 0x1234...abcd" \
  -H "Content-Type: application/json" \
  -d '{
    "to": "user@example.com",
    "subject": "Hello from AI!",
    "text": "Sent autonomously."
  }'
50+
Agents
105K+
Emails Sent
$0.001
Per Email
0
API Keys Needed

What is x402?

x402 is a protocol that lets machines pay for services using HTTP status code 402 (Payment Required). When an AI agent needs to send an email, our API tells it the price and wallet address. The agent pays with USDC on Base blockchain, and the email is sent. No accounts. No API keys. Just crypto.

⭐ USDC on Base & Solana ⚡ Instant settlement 🌍 Global access
[ 01 ] How It Works

Two ways to send emails

Choose the method that fits your use case. Both are simple, fast, and reliable.

👨‍💻 For Developers

1

Sign up & get API key

Create account in 30 seconds

2

Add credits

Top up with card or crypto

3

Send emails

Use API key in your requests

🤖 For AI Agents (x402)

1

Agent calls email API

Gets 402 Payment Required

2

Agent pays $1 USDC

On Base blockchain (1 gas fee)

3

Gets 1,000 emails

Balance tracked by wallet address

[ 02 ] Endpoints

All APIs at a glance

Everything you need. Auth via API key or wallet — both work on every endpoint.

Endpoint Price Auth
POST/api/v1/email/send
Send a plain text transactional email
 $0.001 X-API-Key · X-Payer-Wallet
POST/api/v1/email/send-html
Send an HTML transactional email
 $0.005 X-API-Key · X-Payer-Wallet
GET/api/v1/wallet/balance/{address}
Check USDC wallet balance, total credited, and emails sent
 Free none
GET/api/v1/reputation/{address}
Query agent reputation score, tier, and delivery stats
 Free none
GET/health
Service health check
 Free none
[ 03 ] Features

Built for the future

💰

Pay Per Email

No monthly fees or minimums. Send 1 email or 1 million — pay only for what you use.

🤖

AI-Native

First email API with x402 payments. AI agents send emails autonomously with crypto.

⚡

Instant Setup

Get your API key in 30 seconds. Agents start sending with just a wallet address.

🔒

Business Email Only

We block free email providers to protect IP reputation and prevent spam abuse.

🌍

Global Access

USDC on Base works anywhere. No credit cards, no bank accounts, no borders.

📊

Reputation System

Every agent builds a reputation. Higher tiers unlock better rate limits and priority delivery.

[ 04 ] Pricing

Transparent pricing

No hidden fees. No monthly subscriptions. Pay only for what you send.

Basic

$0.001
per email
  • Plain text emails
  • Single recipient
  • API access

Standard

$0.005
per email
  • HTML emails
  • Rich formatting
  • Up to 5 recipients
Popular

Premium

$0.01
per email
  • Priority delivery
  • Open tracking
  • Click tracking

Bulk

$0.0005
per email
  • 100+ emails
  • Batch sending
  • Best value
⭐ For AI agents using x402 payments: $1.00 minimum = 1,000 basic emails
[ 05 ] Reputation

Agent reputation system

Every agent builds a reputation score based on sending behavior. Higher tiers unlock better rate limits and priority delivery. New agents start at Silver.

🥉 Bronze 0 – 25 Basic sending
🥈 Silver 26 – 50 Standard limits (default)
🥇 Gold 51 – 75 Priority delivery
💎 Platinum 76 – 100 Highest limits & support
[ 06 ] Use Cases

Who uses MailerAstro?

From solo developers to autonomous AI systems.

🚀

Startups & SaaS

Send transactional emails without monthly fees eating into your runway.

  • Welcome emails
  • Password resets
  • Notifications
🤖

AI Agents

Autonomous agents that send emails without human setup. Pay with crypto, send instantly.

  • Scheduling assistants
  • Customer support bots
  • Workflow automation
💻

Side Projects

Building a weekend project? Don't pay $20/month for 10 emails. Pay $0.01 instead.

  • Hobby apps
  • MVPs & prototypes
  • Personal tools
[ 07 ] Agent Discovery

Find us automatically

AI agents and MCP-compatible clients can discover MailerAstro through these channels.

🔌

MCP Server

6 tools · Claude, GPT, Cursor compatible

→
🔍

x402 Resource Discovery

/.well-known/x402.json

→
🤖

Agent Instructions

/llms.txt

→
⭐

Agent Astro Demo

Watch an AI agent send emails autonomously

→
[ 08 ] FAQ

Frequently asked questions

What is MailerAstro?
MailerAstro is an email API that lets you send transactional emails on a pay-per-email basis. Unlike traditional providers with monthly subscriptions, you only pay for what you send.
What is x402 and why does it matter?
x402 is a payment protocol using HTTP 402 status code. It allows AI agents to pay for services with cryptocurrency without needing accounts or API keys. This is crucial for autonomous AI systems that need to operate without human intervention.
Why can't I use Gmail or Yahoo addresses?
We require business email addresses to maintain high deliverability and protect our IP reputation. Free email providers are often used for spam and abuse. This ensures your emails actually reach their destination.
What blockchain do you use?
We use Base (Coinbase's L2 network) and Solana for payments. Transactions cost less than $0.01 and confirm in seconds. We accept USDC stablecoin for predictable pricing.
Do I need cryptocurrency to use MailerAstro?
No! If you're a developer, you can sign up with a traditional account and add credits via card. x402 crypto payments are optional and designed specifically for AI agents.
Is there a minimum purchase?
For x402 payments, the minimum is $1.00 (gets you 1,000 basic emails). This reduces blockchain transaction overhead. For API key users, there's no minimum — add any amount.
What is the MCP server?
MCP (Model Context Protocol) lets AI assistants like Claude, GPT, and Cursor use MailerAstro as a native tool. Agents can send emails, check balances, and query reputation scores directly through their MCP client — no integration code needed.

Ready to send emails?

Get started in under a minute. No credit card required.

Create Free Account → View Agent Demo