Litmus

Litmus is the long-standing standard for previewing how a marketing or transactional email actually renders across Gmail, Outlook, Apple Mail, mobile clients, and dark-mode variants. Pre-send checklist catches broken links, missing alt text, spam triggers, image weight, and load time. Build, Proof, and Analytics modules cover authoring, review, and post-send heatmaps.

At an early stage the deciding factors are what the free tier actually covers, what the first paid invoice looks like, and how much of a founding engineer's week the setup costs. Feature depth that only matters at a million sends a month is noise until it is not.

Against a waitlist, a launch announcement, onboarding email, and the first transactional sends, Litmus covers developer experience and webhook coverage, and does not cover scheduling and SDK breadth. Whether that gap matters depends on how central those are to the build.

• Free tier: 7-day free trial; no permanent free tier on the main paid plans
• Best published rate per 1,000: Tiers not published in comparable form
• Starts at: Basic plan listed on the public pricing page; exact figure varies by region and is sales-driven on higher tiers
• DX score: 8/10
• Deliverability: Not applicable; preview and QA, not a sender.
• Operating since: Not published
• Scheduling: No
• SDKs: None
• Webhooks: Yes

Not applicable; preview and QA, not a sender.

Marketing and lifecycle teams that need pixel-accurate previews across every major client before sending.

Solo developers sending only plain-text or simple transactional email.