Emailens vs Mailpit

Emailens previews HTML email rendering across 21 email clients and checks compatibility across 298 CSS and HTML features. It scores compatibility from 0 to 100 per client and provides rendered screenshots and simulated dark mode variants. Inputs include HTML, React Email JSX, MJML, and Maizzle. Developers can use a web app, REST API, MCP server, GitHub Action, or standalone @emailens/engine package. Campaign HTML can be imported from a view-in-browser link; Mailchimp URL import is marked verified, while other listed platforms require pasted HTML. Emailens discusses merge tags for Mailchimp, Klaviyo, HubSpot, Braze, and Salesforce Marketing Cloud. The free plan costs nothing and includes 30 simulated previews per day, all 21 clients, one monitored domain, seven-day audit history, and three AI Fixes. Paid plans are Dev at $9 a month, Pro at $19 a month, and Team at $49 a month. Emailens says unsaved previews are processed in memory and authenticated previews and screenshots are purged after 30 days.

Mailpit is a free, open-source tool for checking email content and SMTP delivery without sending messages to real addresses. It runs a local SMTP server alongside a web interface and REST API, and is available for Linux, macOS, Windows, Docker, and self-hosted deployment. The interface displays formatted HTML, source, text, headers, raw messages, and MIME attachments with image thumbnails. Checks include HTML and link testing, message screenshots, and optional SpamAssassin scoring. The API can access, search, send, delete, tag, and release messages; messages can also be relayed, forwarded, or used to trigger configurable SMTP errors. Mailpit can send message-summary webhooks and offers a Cypress package for integration tests. The web UI and API can use HTTPS and basic authentication; SMTP supports optional authentication and TLS. By default, SMTP listens on port 1025 without encryption or authentication. Mailpit keeps the most recent 500 messages by default.