Email Testing
Resend has quickly become the developer-favorite transactional email API — clean SDK, React Email template support, and a generous free tier. But email is one of the most undertested parts of most applications. Password reset emails that don't send, welcome emails with broken links, and invoice emails with wrong
Testing
Playwright can automate the browser half of email flows—fill out forms, trigger emails—but it can't read inboxes. Connecting Playwright to IMAP lets you complete the loop: trigger an action in the browser, wait for the email to arrive via IMAP, extract the OTP or link, then
Testing
SendGrid and AWS SES both offer sandbox modes for testing without sending real emails. Beyond sandbox, you need to test delivery event webhooks (bounce, complaint, open, click) and mock the SDK in unit tests. This guide covers the full testing stack for both providers. What Transactional Email Testing Covers Testing
Testing
SPF, DKIM, and DMARC misconfigurations are the most common reason transactional emails land in spam. This guide shows how to validate these DNS records in CI so you catch deliverability regressions before they reach production users. We cover automated DNS checks, DKIM signature verification, and integration with GitHub Actions. Why
Testing
MailHog is the classic local SMTP catcher—simple, lightweight, widely used, and no longer maintained. Mailpit is its modern replacement: faster, ARM-native, with a cleaner API and better CI support. Mailtrap is the cloud-hosted option with spam analysis and team collaboration. This comparison covers all three so you can pick
Testing
Mailtrap's Email Testing API lets you write real assertions against captured emails in Node.js—subject line, HTML body, attachments, spam score—without sending anything to real inboxes. This guide shows how to integrate Mailtrap into Jest tests and CI pipelines so every code path that sends email
Testing
Email testing is more than "did it send?" Good email testing covers HTML rendering across clients, spam score validation, deliverability checks, template regression, and the full user journey from trigger to action. This guide covers the complete email testing pyramid with practical tooling and CI strategies. Key Takeaways
Testing
SendGrid powers email delivery for many production applications. Testing SendGrid integration involves mocking the API client for unit tests, using SendGrid's sandbox mode for integration tests, and testing Event Webhooks for delivery tracking. This guide covers all three layers with Node.js examples. Key Takeaways Enable sandbox mode
Testing
Nodemailer is the most popular Node.js email library. Testing Nodemailer flows has two approaches: mock the transporter entirely (unit tests) or use Ethereal's fake SMTP server (integration tests). This guide covers both approaches, with Jest examples for testing email content, attachments, and error handling without sending real
Testing
MailHog is an open-source local SMTP server that captures all outgoing emails and exposes them via a web UI and HTTP API. No signups, no internet connection required, and no risk of emails reaching real users. This guide covers running MailHog in Docker, asserting on captured emails via its HTTP
Testing
Mailtrap provides a fake SMTP inbox that captures outgoing emails so they never reach real users during testing. Beyond just trapping emails, its API lets you fetch email content, assert on subject and body, check spam scores, and validate HTML rendering. This guide covers the full Mailtrap testing workflow for