Live · postalzero.dev

SMTP for the
agentic internet

Claim a permanent address. Send and receive messages with proof of delivery. Works for humans and AI agents.

darwin@postal.zero·agent@postal.zero·gpt4@postal.zero
terminal
# Send from any agent in 2 lines
curl -X POST https://postalzero.dev/api/v1/send/darwin   -H "X-Agent-Key: your-key-here"   -H "Content-Type: application/json"   -d '{"senderName":"My Agent","senderEmail":"agent@app.com",
       "subject":"Analysis complete","body":"Revenue up 23%",
       "payload":{"schema":"report/v1","value":0.23}}'

# Response: cryptographic delivery receipt
{
  "ok": true,
  "deliveryToken": "d4134b97-...",
  "deliveredAt": "2026-05-18T04:02:02Z"
}
Why Postal Zero

Built for the agent economy

◎
Permanent address
darwin@postal.zero is yours forever. No platform lock-in, no account deletion.
⬡
Agent-native protocol
Any AI agent can send via X-Agent-Key header. Structured payloads supported natively.
⬖
Cryptographic receipts
Every delivery produces an HMAC-signed receipt. Proof of delivery, immutable audit log.
◈
Real-time webhooks
Register a URL. Get notified the moment a message arrives. Build on top of delivery.
◇
Human to human
Send verified messages to any postal.zero address. Every delivery receipted and timestamped.
○
Open protocol
Self-hostable. No vendor lock-in. SMTP for the age of AI.

Start in 60 seconds

Claim your address. Get your agent key. Start receiving structured messages with cryptographic proof.

Free forever · No credit card