A live email address, a dedicated inbox and its own calendar — reachable over REST, MCP and IMAP/SMTP. We run the mail infrastructure end to end, so there is no relay in the path.
Provisioning inbox
Everything a real mailbox needs
Pick a username and one click mints a real mailbox at username@kleevee.com, ready for your agent.
Integrations
REST and MCP, any framework
MCP tools
Drop the server into Claude, Cursor or your own loop.
Calendar actions
Free/busy, invitations and RSVPs.
Delivery telemetry
Per-recipient SMTP results.
Your agent reads, replies and books over REST or MCP. Kleevee never writes the content.
Live activity
Every action, as it happens
Every accepted message, delivery attempt and RSVP lands in the log, in real time.
Send, receive, thread, schedule and prove delivery — on SMTP servers Kleevee writes and runs. No relay sits between your agent and the recipient.
dana@northwind.com
Are you free Thursday afternoon?
sales@acme.com
Thursday 14:00–14:30 is open. Invitation attached.
dana@northwind.com
Accepted — see you then.
Threads that hold. References, In-Reply-To and Message-ID are tracked per inbox, so a reply three weeks later still lands in the same conversation.
Free/busy, answered. Ask for the next opening and get real slots back, already checked against every event the inbox owns.
Signed on the way out. DKIM, SPF alignment and DMARC policy are applied per domain before a byte leaves the queue.
Delivery you can prove. Each recipient carries its own SMTP result, retry schedule and bounce class — streamed to your webhook as it happens.
Point an MCP client at the server or call the REST routes yourself. Same API key, same inboxes, same scopes and the same limits either way.
A tools-only server over Streamable HTTP. Thirty-six tools, no SDK to install, no session to keep alive.
{ "mcpServers": { "kleevee": { "type": "http", "url": "https://kleevee.com/api/mcp", "headers": { "Authorization": "Bearer klv_…" } } } }
…and 16 more, for attachments, domains, webhooks and usage.
Plain JSON over HTTPS. Keys can be scoped to a permission set and locked to a single inbox.
curl -X POST $APP/api/v1/inboxes/$ID/messages \ -H "Authorization: Bearer $KEY" \ -d '{"to":["dana@northwind.com"], "subject":"Thursday","text":"14:00 works."}'
Kleevee never writes a word of it. The tools do what your agent asks, and nothing else.
Kleevee supplies none of the words. It supplies the address the question arrived at, the calendar that had the answer, and the wire that carried the reply back.
dana@northwind.com
Quick sync this week?
Hi — are you free Thursday afternoon for a 30 minute walkthrough? Anything after lunch works on our side.
Infrastructure only — every word above came from your inbox.
Thursday
sales@acme.com
Invitation delivered
Each inbox is a real address with its own threads, calendar, send limit and scoped key. They never share a queue, and a key for one cannot send as another.
sales@acme.com
Books demos straight into its own calendar.
support@acme.com
Answers in-thread, escalates when it cannot.
recruiting@acme.com
Finds a slot both panels can actually make.
research@acme.com
Sends digests and files what comes back.
31,400
meetings booked from one inbox
“Our SDR agent stopped needing a human in the loop the day its inbox got a calendar of its own. It reads the thread, checks Thursday, sends the invite.”
Dana Okonkwo · VP Revenue Operations, Northwind
No SES, no SendGrid, no Mailgun, no Postmark, no Resend. The MX listener, the queue, the signer and the retry schedule are all ours.
A raw TCP SMTP server on port 25 accepts your mail. Nothing forwards it in.
Outbound resolves the recipient's MX and talks to it. There is no relay in the path.
Every message is durable before it is accepted, and claimed by exactly one worker.
DKIM keys are generated per domain and the signature is applied inside the queue.
VERP return paths and DSN parsing separate a hard failure from a temporary one.
Per-domain warm-up curves, concurrency caps and suppression lists we manage ourselves.
Every plan includes the whole platform — mailbox, calendar, MCP server, webhooks and delivery telemetry. The tiers only change how much of it you get.
Custom domains, DKIM keys and dedicated IPs are provisioned by Kleevee — there is no third-party account to open.
If the answer you need isn't here, the API reference goes considerably deeper.
No. Kleevee does not run, host or write agents, and it never composes a message, picks a time or decides whether to accept an invitation. It gives the agent you already built a real mailbox, a calendar and the mail infrastructure underneath, reachable over REST, MCP and IMAP/SMTP. Every word and every decision is yours.
None of them, anywhere in the core path. Kleevee runs its own MX listeners on port 25, its own submission service on 587, and its own SMTP client that delivers directly to the recipient's mail exchanger. Routing, retries, bounce handling, DKIM signing and reputation are all ours.
You pick a username when you sign up — say alex, which registers alex@kleevee.com to your account. It is immediately a live, workable address with its own threads and calendar. In the free plan, your username is permanent and fixed to @kleevee.com.
Yes, on any paid plan. Add your custom domain or subdomain (e.g. acme.com or mail.acme.com), publish the DNS records we generate — ownership TXT, MX, SPF, a DKIM key that is unique to you, and DMARC — and hit verify. After that your inboxes can be sales@acme.com or ai@mail.acme.com.
Every outgoing message carries a VERP return path, so an asynchronous DSN maps back to the exact recipient. Hard bounces and complaints add the address to your suppression list; soft failures retry with backoff. Synchronous 5xx rejections take the identical path, so the outcome is the same either way.
SPF, DKIM, DMARC and forward-confirmed reverse DNS run on every message, attachments are screened before any bytes are written, and spam and prompt-injection signals are scored and handed to your agent. Suspected spam is filed to a spam folder rather than deleted — silently dropping a customer's mail is not something infrastructure should do.
HMAC-signed webhooks, retried with backoff until acknowledged. The signature covers the timestamp and the exact body, and retries resend byte-identical payloads, so a signature you verified once verifies on every attempt.
That's the normal case. An account holds as many inboxes as your plan allows — sales@, support@, recruiting@ — each with its own threads, calendar, send limit and, if you want, its own scoped API key, so a compromised key for support@ cannot send as sales@.
One API call and your agent has a mailbox, a calendar and somewhere to be reached. No relay, no second vendor, no waiting on a sales call.
Free tier, no card. Kleevee-hosted address in under a minute.