Client domains (sub-tenancy)

If you're an agency or a platform, client domains let each of your customers send from their own address, with their own DKIM keys, their own suppression list, and their own reputation score measured separately from everyone else's. Provision a client, hand back the DNS records, verify them, then send scoped to that client.

Send as a client

Scope any request to a client with mail.withSubTenant(id) (SDK) or the X-Rootmail-Subtenant header (HTTP). The client's contacts, suppression list, audit trail, and reputation all stay their own.

const client = await mail.subTenants.create({
  name: "Sunset Villas",
  sendingDomain: "sunsetvillas.com",
});
// hand client.dns_records to your customer, then:
await mail.subTenants.verify(client.id);

await mail.withSubTenant(client.id).messages.create({
  to: "guest@example.com",
  subject: "Your booking is confirmed",
  html: "<h1>See you soon!</h1>",
});

The scope applies to READS as well as sends. With the header set, listing messages, or asking for analytics or deliverability, returns that client's numbers alone — so you can build a per-client view without filtering client-side. Leave it off and you get the whole workspace, every client included.

const acme = mail.withSubTenant(client.id);

await acme.messages.list();      // only Acme's mail
await acme.analytics.get();      // only Acme's funnel
await acme.deliverability.get(); // only Acme's reputation

await mail.messages.list();      // everything, all clients

In the dashboard this is the client switcher in the top bar: pick a client and every section narrows to them until you leave.

• Each client's bounces and complaints are scored on their own, so a reputation problem points at the client causing it.
• Everything rolls up to you for billing and oversight.
• Client domains are sold per-domain — buy them with a plan or on their own.