Get access to email

Transactional email is allowlist-gated and founder-approved — it is not instant self-serve. This page walks you from zero to your first sent message, including the approval step.

Email is for transactional messages only — sign-in links, receipts, password resets, alerts. Not marketing, not bulk.

The onboarding flow at a glance

1. Create an account & API key — sign up and grab your platform API key.
2. Request email access — one click in the dashboard records your request.
3. Founder approval — a thin.host admin reviews and enables sending (a deliverability / anti-abuse check).
4. Verified sending domain — send from the shared mail.thin.host sender immediately, or verify your own domain.
5. Send — via the REST API, SMTP relay, or the send_email MCP tool.

1. Create an account & API key

Sign up at thin.host. Your platform API key lives in the dashboard under Settings → API Key. The key (th_live_…) authenticates every email send, so keep it secret. The free tier is enough to get started.

2. Request email access

Email is off by default. In the dashboard, open Email (or Settings → Transactional Email → How to request access) and click Request email access. This records the request — no email or support ticket is required.

Once requested, the dashboard shows an Awaiting approval badge with the time you applied. Your request appears in the founder's review queue.

3. Founder approval

A thin.host admin reviews each request — this keeps shared sending reputation clean. Approval is quick for legitimate transactional use; we email your account address when sending goes live. Until then, any send attempt returns email_not_enabled.

You can check your status any time on the dashboard Email page — the badge flips from Not enabled to Email enabled once you're approved.

4. Verified sending domain

Your from address must use a verified domain:

• Shared domain (works immediately after approval) — omit from and messages go out as no-reply@mail.thin.host. DKIM, SPF, and DMARC are already configured.
• Your own domain — verify a custom sending domain in platform settings, then send from it.

A from address that doesn't match a verified domain returns invalid_from_domain — surface it to the user, don't retry.

5. Send your first email

Once approved, pick any of the three transports — the same allowlist, domain, suppression, and rate-limit gates apply to all of them.

REST API

curl -X POST https://thin.host/v1/emails \
  -H "X-Platform-API-Key: th_live_your_key" \
  -H "Content-Type: application/json" \
  -d '{
    "to": "user@example.com",
    "subject": "Your sign-in link",
    "text": "Click here: https://app.example.com/login?token=..."
  }'

# → 202 { "id": "...", "status": "sent", "to": "user@example.com",
#          "from": "no-reply@mail.thin.host" }

SMTP relay

Issue per-app SMTP credentials from the dashboard (Email → SMTP credentials — only available after approval). The password is shown once at issue time.

import smtplib
smtp = smtplib.SMTP("smtp.thin.host", 587)  # STARTTLS
smtp.login("your_smtp_username", "your_smtp_password")
smtp.sendmail(from_addr, [to_addr], message)

MCP tool (send_email)

Download the ready-to-install .mcpb package from the dashboard (Email → Claude Desktop MCP package) and open it with Claude Desktop. Your agent can then call send_email directly. See the MCP Tool Reference for parameters and error codes.

Why the approval gate?

Deliverability is a shared resource. Founder approval and the suppression/rate-limit gates keep the sending pool healthy for everyone — which is what keeps your messages landing in the inbox. The gates you'll encounter:

Want a marketing-level overview? See the transactional email use-case page. There's also a drop-in Claude skill that wraps the precondition check and the send call.