Branded, reliable transactional email — provider comparison + custom SMTP + templates

[Muawiya-contact]

Detailed plan for real, branded auth email (supersedes #152). Today Supabase's built-in SMTP is rate-limited (~a few/hour, "testing only"), can't be branded (generic sender), and locks template editing — so confirmation/reset mail is unreliable and doesn't look like it's from us.

Goal

Emails that (a) actually deliver, and (b) come from "One Concept — by Coding Moves" with a branded template, so users trust them.

What emails the app actually sends

Auth transactional only — Confirm signup, Reset password, (optional Magic link). Daily reminders are push notifications, not email. So volume is just signups + resets → a few–tens/day early on. A free tier covers a very long runway (thousands of signups/month).

Two parts

• (A) Delivery — config, not code. Set custom SMTP in Supabase → a transactional provider. This one change removes the rate limit, lets us send from our own domain, AND unlocks template editing.
• (B) Branding — code (templates). Once (A) is on, Supabase → Auth → Email Templates becomes editable; we write branded HTML (logo/wordmark, app colors, clear CTA button, footer) using Supabase vars ({{ .ConfirmationURL }}, {{ .Token }}, {{ .SiteURL }}).

Provider comparison — free vs paid

For low-volume transactional (our case). Verify current terms before signup.

Provider	Free tier	Paid (entry)	Notes
Resend ⭐	3,000/mo (100/day), 1 domain	~$20/mo → 50k/mo	Best DX, easy DKIM, clean dashboard. Recommended.
Brevo (Sendinblue)	300/day (~9k/mo)	~$9–25/mo	Generous daily free; SMTP included.
Mailjet	6,000/mo (200/day)	~$15/mo → 15k	Solid free monthly cap.
SendGrid (Twilio)	100/day (~3k/mo)	~$20/mo → 50k	Reduced free tier; fine for transactional.
Amazon SES	~3,000/mo free for 12 mo	$0.10 per 1,000	Cheapest at scale, but more setup (leave sandbox, DNS) + ops.
Postmark	Trial only (100 test)	$15/mo → 10k	Excellent deliverability; no real free tier.
Mailgun	Trial, then pay-as-you-go	~$0.80 per 1,000	Flexible; free tier weak.

Takeaway: for our volume, any free tier lasts a long time. Resend free (3,000/mo) is the recommended balance of ease + headroom; SES wins only when you're sending large volumes and don't mind the setup.

Prerequisite: a sending domain

To send as "One Concept" (and avoid spam), verify a domain (e.g. oneconcept.app) with SPF + DKIM + DMARC records. One domain purchase also unlocks the custom API domain (#170) — buy once, use for both.

Steps

1. Pick a provider (default: Resend) and sign up.
2. Add/verify the sending domain (SPF/DKIM/DMARC DNS records).
3. Supabase → Project Settings → Authentication → SMTP Settings: enable custom SMTP, enter the provider's host/port/user/pass; set Sender name = One Concept, Sender email = noreply@.
4. Supabase → Authentication → Email Templates: paste the branded HTML (Confirm / Reset / Magic link).
5. Send a test signup + reset; confirm delivery, branding, and that links work (the /reset-password page already handles the recovery flow).

Acceptance

• Confirmation + reset emails deliver reliably (no hourly cap), arrive from a branded "One Concept" sender on our domain, and render the branded template. Signup/reset works end-to-end.

Ownership

• Provider signup, DNS records, Supabase SMTP settings → owner (I can't access DNS/dashboards).
• Branded HTML templates + a docs/EMAIL_SETUP.md checklist → I can produce these on request.