Emailens vs MailTester

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.

MailTester checks why email may reach spam and returns a deliverability score out of 10. To run a test, generate a disposable address, send the message there and receive a report in seconds. Scoring starts at 10, subtracts points for detected issues, and explains penalties with suggested fixes. Authentication checks include SPF, DKIM, DMARC, domain alignment, reverse DNS and forward-confirmed reverse DNS. Sending IPs are checked against Spamhaus, SpamCop, Barracuda and other DNS blocklists. Content analysis covers HTML, text-to-image ratio, links, subject, List-Unsubscribe and Message-ID. Rspamd supplies a spam score and triggered rules. Newsletter checks include one-click List-Unsubscribe under RFC 8058, message size and text-image ratio. MailTester offers web, API and self-hosted platforms. Its API creates test addresses and reads report status and scores as JSON. The free plan costs nothing, needs no account and provides 25+ checks per test.