Multi-tenant email + LinkedIn API for SaaS builders

The problem

You're building a SaaS product where each customer needs:

• Their own email inbox (or several) — sending and receiving from real, addressable addresses
• Their own LinkedIn account connected so the agent works leads from their personal network
• Activity, quotas, and audit trails kept isolated from other customers
• Billing and usage reporting that maps cleanly to your tier structure

Most email APIs are single-tenant. Postmark has "Servers" but isolation is by convention. Resend assumes one company. SendGrid technically supports subusers, but you're building IAM on top of their primitives.

You shouldn't be writing the multi-tenancy layer. MyAgentMail's primitives ARE the multi-tenancy layer.

What MyAgentMail gives you

• Workspaces — isolation containers under your tenant. Spin up one per customer or per environment.
• Scoped API keys — wk_... (workspace master), ak_... (per-inbox), distinct from your own tk_... master key. Customers can't access each other's data even if they get a leaked key.
• Per-tenant rate limits — burst (10/sec), sustained (200/min), llm (60/min) buckets enforced per tenant, not per global pool. One noisy customer can't starve the others.
• Per-customer LinkedIn quota — sessions, daily action caps, intent-signal counts all scoped to the workspace. Tier-up = bigger bucket.
• Webhook routing per workspace — your customer's webhooks fire to their endpoint, not yours.
• Stripe-style metadata flow — webhook events carry workspaceId, so your billing pipeline can attribute usage cleanly.

Architecture sketch

┌─────────────────────────────────────────────────┐
│  Your SaaS app                                  │
│  Customer signs up → you provision a workspace  │
│  → you store their workspace_master_key         │
│  → all their actions scoped to their workspace  │
└─────────────┬───────────────────────────────────┘
              │
              ▼ POST /v1/workspaces (X-API-Key: tk_<your-master>)
              │
        MyAgentMail
              │
              ├── workspace A
              │     ├── inbox: [email protected]
              │     ├── linkedin session 1
              │     └── webhook → customerA's app
              │
              ├── workspace B
              │     ├── inbox: [email protected]
              │     ├── linkedin session 2
              │     └── webhook → customerB's app
              │
              └── ...

import { MyAgentMail } from "myagentmail";
const platform = new MyAgentMail({ apiKey: process.env.MAM_TENANT_KEY });

// On customer signup:
const ws = await platform.workspaces.create({
  name: customer.companyName,
});
// ws.masterKey is the wk_... — store it on your customer row.

// Use that key to provision per-customer inboxes:
const customerMam = new MyAgentMail({ apiKey: ws.masterKey });
await customerMam.inboxes.create({ username: "agent", domain: customer.domain });

What this saves you

Building a real multi-tenant infrastructure costs 3-6 months. MyAgentMail's already done it.

White-label and reseller considerations

• Custom domain per customer: each workspace can verify and own its own custom domains. Customer's mail goes from [email protected], not *.myagentmail.com.
• Webhook signing per workspace: each subscribed endpoint gets its own HMAC secret so even if you proxy webhooks, the customer can verify they came from us.
• Audit trails: every API call is logged with workspace_id, queryable via the metrics endpoint.

Where this is NOT the right fit

• You're not building multi-tenant SaaS — you're shipping internal tooling for one team. Use the simple Cold outreach shape instead.
• You need WhatsApp / Telegram / Messenger. Unipile covers more channels; we don't.
• You need a UI. We're API-first. The outreach starter is open-source if you want to fork rather than build.

Pricing

Email: $5/month per inbox provisioned. LinkedIn: $29-$199/month depending on tier (Solo / Team / Agency). Workspaces are free — you pay for the resources inside them. See /pricing for the full breakdown and /email + /linkedin for module-specific details.

Related

• Sales agent (use case)
• Cold outreach (use case)
• MyAgentMail vs Resend
• Multi-tenant Email SaaS (deep dive)