KeyKeeperFOR DEVELOPERS
One mail service. More ways to build.
Use REST or MCP to give your application a real mailbox. We’re growing that foundation into a lightweight transactional email service on our own infrastructure.
Receiving and reading are free. New agents start with zero sending credits. A $1 card or native USDC top-up buys 10,000 mail credits for standard sending. New senders start with up to 10 recipients/day and 3/minute; the plan limit applies if lower. Buying credits does not raise sending permissions. Higher-volume use has separate pricing and review. See /docs/sending-safety. Broad transactional sending is being prepared for a controlled pilot.
BUILD AGAINST THE CURRENT API
Your mailbox is
a programmable interface.
Create an agent account for your integration. Use its key to list and read incoming mail. Accounts with prepaid mail credits can submit messages, including attachments, from their own mailbox address.
- Keep the key on your serverDo not embed it in public frontend code or URLs.
- Make retries safeReuse the same Idempotency-Key and identical payload after a timeout.
- Account for recipientsOne mail credit per accepted recipient. Sending is capped per account.
Send with prepaid mail credits
curl --fail-with-body https://keykeeper.world/api/v1/agent/send \
-H "Authorization: Bearer $KEYKEEPER_API_KEY" \
-H 'Content-Type: application/json' \
-H 'Idempotency-Key: unique-message-001' \
-H 'User-Agent: MyAgent/1.0' \
-d '{"to":"[email protected]","subject":"Hello","body":"A message from my agent."}'An accepted response means SMTP accepted the message. It is not a delivered event. If the outcome is unknown, keep the original key and reconcile before trying a new send.
TOWARD A RESEND ALTERNATIVE
A useful pilot comes before
a broad sending launch.
These are the current capabilities and remaining readiness gates for wider transactional sending.
| Capability | Current state |
|---|---|
| Mailbox registration, receiving and reading | Available |
| Signed incoming-mail webhooks and retry history | Available; free to receive |
| Authenticated REST / MCP sending | Prepaid mail credits; from $1 |
| Recipient accounting and idempotent retries | Available |
| Mailbox and domain sender authorization | Available |
| Scoped keys, allowed identities and integration budgets | Next priority |
| Delivery events, bounce handling and suppressions | Available; see the delivery reference for scope |
| Custom domains with per-domain DKIM | Personal: one domain + 10 aliases |
| Higher-volume developer sending | Separate pricing and operator review |