Tool #3 · What we install in your business · In client work

Transactional Email APIResend

Website quote requests and app verification codes land in the inbox—with preview builds blocked from spamming real sales teams.

Last reviewed: 2026-10-22 · Status: In client work

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Full stack receipt#3 · In client work · reviewed 2026-10-22
#3Transactional Email API

Resend

In client work
1. What we use it for: We use Resend’s HTTP email API to deliver website quote-form leads to client sales inboxes and send transactional password-reset codes from backend APIs.
2. Client use case · A print and signage companyState: live
Problem

Quote-form submissions from the 49-page site needed reliable delivery to the sales inbox without letting staging or preview deploys email sales reps during automated browser tests.

What the tool did

Wired the Cloudflare Worker `/api/quote` handler (`worker/index.ts`) to Resend with an explicit environment guard that refuses to send emails from preview hosts.

Result

Live since 2026-10-15; launch test lead verified as "Delivered" to the sales inbox while preview environments stay safely blocked.

2. Client use case · RiseSyncState: live
Problem

The RiseSync iPhone coaching app needed transactional email delivery for password-reset verification codes from its Fastify backend on Railway.

What the tool did

Configured the Fastify authentication service (`backend/src/services/auth.ts`) to send password-reset codes through Resend during Milestone 1.

Result

Live in TestFlight builds 7–9 (submitted 2026-10-22), currently sending via Resend’s shared sender until the client’s custom domain DNS is finalized.

3. What it costs us or the client

$0/month on Resend Free (up to 3,000 emails/month, 100/day) and $20/month on Pro (50,000 emails/month) (as of 2026-10-22).

4. Setup notes (how it is wired in)

Called via a single `fetch` POST from a Cloudflare Worker or Fastify backend using SPF/DKIM records on the verified sending domain and a strict hostname check that disables outbound delivery on non-production URLs.

5. What broke & how it was handled

On RiseSync, the client’s own Resend account and custom domain DNS were still pending at Milestone 1 cutover, leaving password-reset emails on Resend’s shared test sender (which only delivers to the registered developer address until DNS is verified). On website builds, Playwright smoke tests will flood the sales inbox unless preview hosts are explicitly blocked in the Worker.

6. What we compared it against & why we picked it

Compared against SendGrid (which we still run for 79 legacy transactional templates at a nonprofit education center and in our pFrame Python API), Mailgun (merged as a pending sender for a members’ dinner club), and a temporary Gmail API sender. We picked Resend for new Workers and apps because its REST API works natively in edge runtimes with clean delivery logs.

7. Last reviewed: 2026-10-228. Video / tutorial: Covered in Episode 3: "Moving a Service Business Off Wix to Astro + Cloudflare Workers"
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