Manual testing persists from fragmented workflow

Manual testing persists because email is still built and owned as a fragmented craft workflow, not as a software system with a live test harness. Teams usually duplicate old HTML, paste it into an ESP like Marketo, send test emails by hand, and only run deeper checks when a template changes. That makes one off previews valuable, but it leaves no always on layer watching for Gmail or Outlook rendering changes after an email is already live.

• The market leader was built around previews, not background monitoring. Litmus is positioned first as a testing and preview product, while Parcel is built first for creating email code. That split helps explain why teams buy tools to inspect renders on demand, but still do not have automated recurring checks running quietly in production.
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• Most teams still work from a small library of reused templates, so they test only when making obvious changes. At Figma, the team duplicates a prior file, swaps content, copies code into Marketo, and uses Litmus mainly for major layout updates. That is efficient enough to preserve manual habits even when everyone knows email clients can change underneath them.
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• Email code breaks in ways that sit between product, marketing, and infrastructure. A developer can fix a component once and update many emails, but if the code still has to be exported into a separate sending platform, there is no single system responsible for continuously checking every live message. That handoff gap keeps testing episodic and manual.
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The next step is turning email QA from a before send task into an always on monitoring layer tied directly to components, journeys, and ESPs. As creation tools and sending platforms merge, the winning products will be the ones that recheck live emails automatically, catch client side breakage early, and push fixes across every template from one place.