Litmus

What it does

Litmus is an email QA platform that renders a single email across 90+ real email clients and devices — Outlook desktop, Gmail, Apple Mail, dark mode, and more — using actual virtual machines rather than simulated previews, so teams catch broken layouts before sending. It also flags accessibility issues, checks links, runs spam tests, and reports post-send engagement analytics. Higher tiers add a drag-and-drop email builder, dynamic content and personalization blocks, and built-in proofing and approval workflows for teams that need sign-off from multiple stakeholders before a send goes out.

Who this helps

• Email marketing teams sending design-heavy HTML campaigns to lists with meaningful Outlook or enterprise-email usage

• Agencies that need client sign-off workflows and shared proofing built into the QA process

• Brands that got burned by a broken layout in one major email client and want to stop guessing

• Teams needing accessibility checks — alt text, contrast, screen-reader compatibility — on every send