Litmus

Litmus is an email testing and deliverability tool for marketing teams that previews campaigns across clients and monitors inbox placement, owned by Validity.

Litmus is an email testing and deliverability tool for marketing teams that need every campaign to render correctly and reach the inbox. It previews an email across mail clients before a send, tests it against spam filters, and then watches placement, reputation and rendering after the send. Litmus Software, Inc. built it in Boston, where it started in 2005, and Validity owns it today. Litmus announced on April 11, 2025 that it was being acquired by Validity, and litmus.com now says on every page that Litmus is part of Validity Engage. Litmus Builder is the editing workspace, with a code editor, a visual editor and a Design Library for shared brand assets. Email Previews show how a message renders across clients and devices, Litmus Test runs the pre-send QA pass, and the Checklist flags spam-trigger content and a missing unsubscribe link. Litmus Spam Testing and the deliverability suite show which mailbox providers are sending a campaign to spam, track SPF, DKIM and DMARC results, report sender reputation beyond what the ESP shows, and raise alerts on blocklists and spam traps through customizable dashboards. Email Analytics reports opens, privacy-impacted opens, read time, device and Dark Mode usage. Litmus Personalize adds countdown timers, progress bars and other live content, and always-on email monitoring catches an email that breaks after it has gone out. Review and approvals, subaccounts, brand settings and user permissions cover the team workflow. Litmus fits enterprise email teams that send at volume through Acoustic Campaign, Adobe Journey Optimizer, Marketo, Campaign Monitor, HubSpot, Klaviyo or Salesforce Marketing Cloud and want QA and deliverability data in one place. Deliverability specialists get placement and reputation monitoring, designers get the builder and the previews, and managers get the review workflow and the analytics. Agencies and multi-brand companies use subaccounts to keep templates and brand settings apart. It is bought as part of Validity Engage through the Validity sales team under one login, and the plan cards list what the Enterprise tier includes. In practice Litmus sits between the sending platform and the send button. A team builds or imports an email, previews it, runs the Checklist and the spam test, routes it through approval, and syncs it to the ESP through the integration for that platform. After the send, the deliverability dashboards and alerts show placement by mailbox provider, blocklist status and authentication results, and Email Analytics feeds engagement data back to the team. Slack is among the integrations, and Google Drive, Dropbox and OneDrive supply images and files into Builder. It sits beside the ESP rather than replacing it, and beside the rest of Validity Engage for teams that buy the wider platform.