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Emailens
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An Email on Acid alternative for the rendering check

Emailens checks your email before your client opens it: a free account gives live previews across all 21 inboxes (five without an account); real screenshots from $19 a month. It does not take a real-client screenshot on every check.

The checker needs a computer screen.

Email on Acid is the better tool if

  • You want a real-client screenshot on every check. Emailens runs every check as a live preview and meters real screenshots.
  • Your team reads screenshots, not code, and a list of CSS findings would not help it.

Emailens is the better tool if

  • You write emails in code (HTML, React Email, MJML or Maizzle) and want to see which CSS fails in which client, with the engine's fix (Free).
  • You want a pull request to fail when an email breaks in Outlook (GitHub Action, Pro).
  • Your AI coding assistant writes emails and should check them before it hands them over (MCP server, Free).
  • You want real-client screenshots when they matter, not on every save (real-device checks, Dev + Real).

Do you keep real screenshots? Yes, metered.

A real-device check screenshots your email in real Outlook on Windows and Mac, Apple Mail on Mac and iPad, Gmail and Yahoo on the web and Android, and Proton: 20 checks a month on Dev + Real, 50 on Pro + Real. Here is the Emailens probe for one feature on real installs, beside our live preview.

border-radius:

Works in 16 of 21 · partial in 4 · not supported in 1

Three clients, picked by one rule: the one where border-radius is not supported, one where it is partial, one where it works. Where it is supported you should see rounded corners.

Outlook Classic

caniemail: border-radius is not supported in Outlook Classic.

Emailens live preview of Outlook Classic Our live preview The same probe in the Emailens live preview of Outlook Classic
Yahoo Mail

caniemail: border-radius is partly supported in Yahoo Mail.

Emailens live preview of Yahoo Mail Our live preview The same probe in the Emailens live preview of Yahoo Mail

Partial support. Shorthand for setting elliptical borders with the slash / notation is not supported e.g. border-radius: 27% 73% 70% 30% / 30% 34% 66% 70%;.

Outlook 365

caniemail: border-radius works in Outlook 365.

Emailens live preview of Outlook 365 Our live preview The same probe in the Emailens live preview of Outlook 365

This Outlook.com install drops the <style> in the head, so only inline styles apply.

Also captured, not counted as evidence (3)

Every account includes one free real-device check in classic Outlook, Outlook for Mac and Apple Mail, after you verify your email and run one preview, while this month's free capacity lasts. How real-device checks work →

border-radius in every client →

The fix for Outlook Classic

Use VML to render rounded buttons in Outlook

after 
<!--[if mso]>
<v:roundrect xmlns:v="urn:schemas-microsoft-com:vml"
  href="https://example.com"
  style="height:44px; v-text-anchor:middle; width:200px;"
  arcsize="14%" strokecolor="#6d28d9" fillcolor="#6d28d9">
  <w:anchorlock/>
  <center style="color:#fff; font-family:Arial,sans-serif;
    font-size:14px; font-weight:bold;">Click Here</center>
</v:roundrect>
<![endif]-->
<!--[if !mso]><! -->
<a href="https://example.com"
  style="background-color: #6d28d9; color: #fff;
         padding: 12px 32px; border-radius: 6px;
         text-decoration: none; display: inline-block;">
  Click Here
</a>
<!-- <![endif]-->
Show the original
before 
<a href="https://example.com"
  style="background-color: #6d28d9; color: #fff;
         padding: 12px 32px; border-radius: 6px;
         text-decoration: none; display: inline-block;">
  Click Here
</a>

The checker needs a computer screen.

A free account opens all 21 clients and keeps your checks for 7 days. Create a free account →

What it costs

  • Email on Acid Basic · 1,000 previews a month $99 a month
  • Email on Acid Premium · 2,000 previews a month, adds HTML code analysis $199 a month
  • Email on Acid Contract · quoted by sales Custom

Read at Their pricing page on 11 Nov 2026

Emailens, by what you need

A free account: 30 checks a day in all 21 clients, kept for 7 days.

Real-client screenshots

Dev + Real is $19 a month, with 20 real-device checks a month. Real-device plans →

The pull-request gate in CI

GitHub Action (Pro). Pro is $19 a month. The pre-send gate in CI, and the history behind every check. See the plans →

Both

Pro + Real is $39 a month, with 50 real-device checks a month.

Sandbox SMTP and the API

Sandbox SMTP (Dev). Dev is $9 a month. Share links for your client's sign-off, a test inbox and an API key. See the plans →

Dev + Real and Pro cost the same: one adds real-client screenshots, the other the pull-request gate in CI.

Row by row

Rendering check
Every email in a live preview of all 21 clients (Free; five without an account)
Email on Acid: Pre-send previews across email clients and devices, now sold as Mailgun Inspect.checked 11 Nov 2026
Real-client screenshots
Real Outlook on Windows and Mac, Apple Mail on Mac and iPad, Gmail and Yahoo on the web and Android, and Proton: 20 checks a month (Dev + Real), 50 (Pro + Real); one free check in classic Outlook, Outlook for Mac and Apple Mail with an account
Email on Acid: Says all its tests run through actual email clients.checked 11 Nov 2026
Which CSS fails where, and the fix
Per-client findings with the engine's fix (Free)
Email on Acid: HTML code analysis, on the Premium and Contract plans.checked 11 Nov 2026
Pull-request gate
GitHub Action (Pro)
Email on Acid: An API for deeper integration with internal tools: submit emails and read the results.checked 12 Nov 2026
AI coding assistants
MCP server (Free)
Email on Acid: Mailgun's MCP server retrieves Inspect rendering and preview test results.checked 12 Nov 2026
Test inbox
A private @try address (Free); sandbox SMTP and API (Dev)
Email on Acid: An Auto-Inbox address: emailed content is processed into a test, with results read through the API.checked 12 Nov 2026

Moving over from Email on Acid

  1. Create a free account and check an email you sent with Email on Acid, in all 21 clients.
  2. Add the GitHub Action, so a pull request fails when an email breaks (Pro).
  3. Point your AI assistant at the MCP server, or run the CLI in your terminal.

Questions

What do I lose moving from Email on Acid?
A real-client screenshot on every check. Emailens runs every check as a live preview and keeps real screenshots for when they matter, metered on the + Real plans. If your team reads screenshots and never the code, that is a real loss.
Can I try Emailens without paying?
Yes. The checker needs no signup: five clients, 3 checks a day, results kept for an hour. A free account opens all 21 clients and keeps your checks for 7 days. It allows 30 checks a day. Every account includes one free real-device check in classic Outlook, Outlook for Mac and Apple Mail, after you verify your email and run one preview, while this month's free capacity lasts.
Which plan does the GitHub Action need?
Pro. The Action's pre-send gate is a Pro feature: on Free and Dev it answers "The pre-send gate is available on the Pro plan."

Sources

Real captures 14 Oct 2026 on 10 installs · caniemail (MIT) via @emailens/engine 0.18.22 · tested upstream 9 Mar 2021 · data last changed 10 Nov 2026

Check an email you sent with Email on Acid

The checker needs a computer screen.

A free account opens all 21 clients and keeps your checks for 7 days. Create a free account →

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