Does signing emails cost anything?

No. Signing is free and unlimited on every plan; only verifications are metered.

Do recipients need an account to verify a message?

No. Anyone can call the /v1/verify endpoint without an API key and receive a confidence score and the agent's identity.

Is a credit card required to start?

No. The free tier requires no credit card, and paid plans can be cancelled anytime.

Eleidon

Secure external messaging. The inbox that can't be phished.

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Feature Eleidon for a year

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About Eleidon

Eleidon is a cryptographic identity layer for email sent and received by AI agents. It lets agents verify inbound emails before acting on them and sign outbound emails so recipients, human or agent, can confirm a message is genuine and unaltered. The product addresses a gap left by DKIM and SPF, which verify domains and servers but not the agent itself.

Setup takes three steps: generate a keypair and register the public key with a claimed inbox, sign each outgoing email with the private key (adding a single header), and let anyone check messages through the /v1/verify endpoint, which requires no API key. Verification returns a result such as verified or fraudulent, a confidence score, the agent's identity and whether the agent owns the inbox, giving an audit trail when disputes arise.

Eleidon is aimed at developers building AI agents that handle email, such as support or order-notification agents. It offers a TypeScript SDK, a Python SDK, an MCP server and a CLI. Signing is free and unlimited, while verification is metered by plan.

Best for

Developers building email-handling AI agents
Teams running customer support or order agents
Agent platforms needing verifiable outbound email
MCP-based agent builders

Pros

Signing is free and unlimited on all plans
Recipients can verify messages without an API key
TypeScript and Python SDKs, MCP server and CLI available
Returns confidence scores and agent identity for each check

Cons

Signature verification relies on senders registering with Eleidon
Verification volume is capped by plan

Pricing

Free plan with 100 verifications per month, then Starter at $9/month (1,000), Pro at $29/month (10,000) and Platform at $89/month (100,000), all with unlimited signing and enterprise options on request.

Eleidon FAQ

Does signing emails cost anything?: No. Signing is free and unlimited on every plan; only verifications are metered.
Do recipients need an account to verify a message?: No. Anyone can call the /v1/verify endpoint without an API key and receive a confidence score and the agent's identity.
Which languages and tools are supported?: Eleidon offers a TypeScript SDK, a Python SDK, an MCP server and a CLI.
Is a credit card required to start?: No. The free tier requires no credit card, and paid plans can be cancelled anytime.