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Supabase sends its own auth emails (confirm sign-up, magic link, password reset, invite, email change, reauthentication) but gives you little control over templates or deliverability. By connecting SenderKit as Supabase’s Send Email Hook, every auth email flows through your SenderKit workspace: you own the templates, you see delivery events in Logs, and you can align the sending domain with your brand.

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One-click setup

1

Open the Integrations page

In the SenderKit dashboard, go to Integrations and click Connect Supabase.
2

Authorize SenderKit in Supabase

You’ll be redirected to Supabase to authorize SenderKit to read your projects and manage auth configuration.
3

Pick a project

Select the Supabase project whose auth emails you want to route through SenderKit. Once confirmed, SenderKit automatically:
  • Mints a signed inbound endpoint — a dedicated URL and signing secret that Supabase will use to deliver hook payloads.
  • Seeds and publishes six auth templates — one for each Supabase auth action (see Template slugs below). Any existing template with the same slug is left untouched.
  • Configures Supabase — patches the project’s Send Email Hook to point at the new endpoint, enables the hook, and increases the project’s email rate limit so SenderKit — not Supabase — governs send volume.
After connecting, auth emails go through SenderKit immediately. To confirm it’s working, trigger a sign-up in your Supabase project and check Logs in the SenderKit dashboard — a message should appear within seconds.
The one-click integration requires hosted Supabase (supabase.com) with a project you manage. If you self-host Supabase, reach out to support@senderkit.com for manual endpoint provisioning.

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Customizing the seeded templates

After connecting, find the six supabase-* templates in Templates and edit them as you would any other template. The seeded defaults are functional — update them to match your brand.
Templates must be published before they send in live mode. The auto-seeder publishes the default versions; any edits you save stay as drafts until you publish.
For best inbox placement, verify a custom sending domain under Channels → Domains so auth emails are DKIM-signed for your own domain rather than the shared tx.senderkit.email address.

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Template slugs

SenderKit maps each Supabase auth action to a template by slug: An unsupported email_action_type returns 200 with no send — Supabase considers the hook handled and does not fall back to its built-in mailer or retry.

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Template variables

Every auth email receives the following variables, which mirror Supabase’s own built-in template variables so you can reuse your existing email copy: At minimum, use {{ConfirmationURL}} for link-based flows and {{Token}} if you display OTP codes.
Supabase’s Send Email Hook payload does not include a pre-built confirmation URL. SenderKit reconstructs it as {SiteURL}/auth/v1/verify?token={TokenHash}&type={action}&redirect_to={RedirectTo}, which is identical to what Supabase’s own email templates produce.

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Limits and notes

  • 5-second timeout. Supabase requires a hook response within ~5 s. SenderKit enqueues the send asynchronously and responds immediately — this is comfortably met.
  • Signature verification. Payloads with an invalid svix-signature header return 401. An unrecognized endpoint token returns 404.
  • 4xx on misconfiguration, not 5xx. If a mapped template doesn’t exist or isn’t published, or the workspace is over quota, the hook returns the real 4xx code (e.g. 404 template_not_found, 402 message_limit_reached). Supabase treats 4xx as a permanent failure and will not retry, so the cause is visible in logs rather than triggering a retry storm. Only unexpected transient failures return 5xx.
  • Unsupported actions are silently accepted. Any email_action_type outside the six above returns 200 with no send.
  • Retries are deduplicated. If Supabase retries a delivery (or a network blip means it never sees SenderKit’s response), the retry won’t send the email again.
  • One endpoint per mode. The Integrations page creates a live-mode endpoint. To test before going live, use a sk_test_ key connection with draft templates — sends are recorded but not dispatched to a provider.

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What’s next

Notify on a database change

App-domain notifications from Supabase row changes — separate from auth emails.

Custom sending domains

DKIM-align auth emails with your own domain for better deliverability.

Templates

How to publish, version, and manage templates.

Logs

Track delivery status for every auth email sent.