Supabase SMTP

Send Supabase Auth emails — confirmations, magic links, password resets — through eusend by configuring custom SMTP in your Supabase project.

Supabase's built-in email service is rate-limited and meant only for testing — in production you must bring your own SMTP provider for auth emails (confirmations, magic links, password resets, invites). Pointing Supabase at eusend gives you DKIM-signed delivery on your own domain, with every auth email visible in your eusend dashboard.

Connect in one click

If you would rather not copy anything by hand, connect Supabase from Settings → Integrations in the eusend dashboard. You authorize eusend against your Supabase organization, pick the project and a verified sending domain, and we write the SMTP settings into that project's auth config for you — along with a raised auth-email rate limit.

The key we create for the connection can only send from the domain you chose, and disconnecting revokes exactly that key and clears the SMTP block again.

The manual setup below stays supported, and is the right choice if you would rather not grant write access to your project's auth configuration.

Connection values

Parameter	Type	Description
`Host`required	`smtp.eusend.dev`	The submission server.
`Port`required	`465`	Implicit TLS. STARTTLS (587) is not supported.
`Username`required	`eusend`	The literal string "eusend".
`Password`required	`eu_live_…`	Any eusend API key.
`Sender email`required	`no-reply@yourdomain.com`	Must be a verified domain.

Setup

Open SMTP settings

In the Supabase dashboard go to Authentication → Emails → SMTP Settings and toggle on Enable Custom SMTP.

Enter the connection

Supabase → Custom SMTP

Host:          smtp.eusend.dev
Port:          465
Username:      eusend
Password:      <an eusend API key, eu_live_…>
Sender email:  no-reply@yourdomain.com   (must be a verified domain)
Sender name:   Your App

Save.

Send a test email

Use Supabase's Send test email button — it exercises the whole path end to end. A delivered test confirms your key and sender domain are correct.

ℹ

The sender email must be an address on a domain you have verified in eusend. An unverified sender domain and a wrong username or key both come back as a 535 — the response text says which.

Adjust the rate limit

Supabase caps auth email throughput separately from your SMTP provider. Under Authentication → Rate Limits, raise "Rate limit for sending emails" to match your expected sign-up volume — otherwise Supabase, not eusend, becomes the bottleneck. eusend's own sending limits still apply on top.

Note on password recovery links

Auth emails are generated and sent by Supabase itself; eusend is only the transport. Customize the templates under Authentication → Emails → Templates in Supabase. Everything eusend adds — DKIM, tracking, suppression — is applied to whatever Supabase hands off.

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