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Multi-tenant email infrastructureMektup is multi-tenant email infrastructure: your SaaS provisions a real, isolated inbox for each of its own customers through one API, while your app and its AI agents keep controlled, scoped access. Each customer sees only their own mailbox - never your account, your other domains, or anyone else's mail. It's the pattern payment platforms use for programmatic accounts, applied to email inboxes.
Your backend creates a mailbox per tenant the moment they sign up - customer-a@yourapp.com, customer-b@yourapp.com, or a full mailbox on each customer's own domain. No separate account per customer, no per-domain signup: every mailbox lives under your single Mektup account and API key.
// a new customer signs up -> give them a real inbox await fetch("https://api.usemektup.com/v1/mailboxes", { method: "POST", headers: { Authorization: `Bearer ${process.env.MEKTUP_API_KEY}`, "Content-Type": "application/json", }, body: JSON.stringify({ domain: "yourapp.com", localPart: customer.slug, // -> acme@yourapp.com webhookUrl: "https://yourapp.com/hooks/mail", }), }); // acme@yourapp.com now sends, receives, and // notifies your app the instant new mail arrives
A transactional email API only sends - there is no inbox behind the address, so a per-customer inbox as a real object simply doesn't exist. Mektup gives each customer a real mailbox that sends and receives over the API, MCP, IMAP, and SMTP. Incoming mail, replies, and full threads for that customer are actually stored and readable - so "the customer's inbox" is a first-class thing your product can build on.
Each customer sees only their own mailbox and its mail. They never see your account, your other domains, your other customers, or each other's messages. You grant scoped access per mailbox, and Mektup enforces the boundary - you don't have to invent a tenancy model, partition storage, or police cross-tenant access yourself.
Every mailbox is reachable over the REST API and the native MCP server with scoped credentials, and each can fire an HMAC-signed webhook on new mail. So a per-customer AI agent can read, triage, and reply within that one customer's inbox only, without touching any other tenant. The same infrastructure serves your code and your AI agents at once.
Mektup runs and operates all the mail infrastructure - real MX, IMAP, SMTP, and DKIM signing - across every tenant. There is nothing for you to host, scale, or keep online, and no mail server tenancy to design. You provision inboxes through an API; Mektup keeps the mail flowing and isolated. Delivery status (sent / deferred / bounced) comes straight from the receiving server's real SMTP response, per message, per tenant.
Multi-tenant email is the backbone for products like: a support desk that gives each client its own reply-to inbox; an AI agent platform where every agent needs a real address; an agency tool running mail for many client domains; or any SaaS that wants "your own inbox inside our app." If your model is product → many customers → each needs a real inbox, that's exactly what Mektup is built for. See also email for your SaaS and shared inboxes for humans and AI.
Yes. Your backend calls one API (or MCP tool) to create a real, isolated inbox per customer - customer-a@yourapp.com, customer-b@yourapp.com, or a mailbox on each customer's own domain. No separate signup per customer; every mailbox lives under your one account and API key.
Yes. Each customer sees only their own mailbox and its mail - never your account, your other domains, your other customers, or each other's messages. You grant scoped access per mailbox, so isolation is enforced by Mektup, not something you build.
A transactional API only sends - there is no inbox behind the address. Mektup gives each customer a real mailbox that both sends and receives over the API, MCP, IMAP, and SMTP, so incoming mail, replies, and threads for that customer are actually stored and readable.
Yes. Every mailbox is reachable over the REST API and native MCP server with scoped credentials, and each can fire a webhook on new mail. A per-customer AI agent can read, triage, and reply within that one customer's inbox only, without touching any other tenant.