Testing transactional email in staging and CI: sandboxes, assertions, rendering checks, and the mistakes a sandbox catches for you.
5 articles
Every captured message gets a score out of 100. This is exactly what goes into it — SPF, DKIM, DMARC, BIMI, List-Unsubscribe, X-Priority and a SpamAssassin pass — with the weight of each rule, what a sandbox result says about production, and how to use the score as a gate in staging.
A share link can now cover an entire project rather than a single message: password-protected, expiring, revocable, in preview or developer mode, and white-labelled on the plans that include it. What a link exposes, and what it never does.
Two small features that go together: a read-only link to a single captured message for a client or a PM, and browser notifications when a new email arrives in a project you follow. Including why we never put a push endpoint in a page.
Mailclutch now follows your system theme. The harder half was the preview: a message whose dark-mode styles assume the client paints a dark canvas renders invisibly in a light reading pane, so we rewrite its colour-scheme queries instead of trusting them.
Why 'just use a test address' fails, what an SMTP sandbox actually intercepts, the six classes of email bug that only show up on a captured message, and how to wire a sandbox into staging and CI without touching application code.
See it on your own mail
Point your staging SMTP at Mailclutch and every message comes back with its headers, its spam score and its authentication results — before a customer sees it.
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