Email on Acid is usually the tool people move to when Litmus gets too expensive, so if you're looking past it, the reason matters more than the shortlist. Find yours below.
Who's writing this: Mailfois is our product and it's one of the options below. It doesn't render emails across clients, which is Email on Acid's core job, and we've tried to be straight about that. Prices are from each company's own site unless stated, in US dollars, checked in October 2026.
What Email on Acid does well
It's worth being clear about this before replacing it. Email on Acid, part of Sinch's email brands alongside Mailjet and Mailgun, previews your email in more than 100 clients and devices, checks accessibility against WCAG 2.2, runs content spam analysis and checks your links and images. Every plan has unlimited users. Basic is $99 a month for 1,000 previews and Premium is $199 for 2,000, with extra previews at $0.15 each. For a team that tests a lot of email, that's good value, and most alternatives that render properly cost the same or more.
What its site doesn't describe is any review or approval workflow. Testing tells you the email works. It doesn't tell you the right people have agreed to send it.
If you want it free
No free tool renders your email in Outlook, Gmail, Apple Mail and the rest the way Email on Acid does. Rendering at that scale costs money to run, so be wary of anything that claims otherwise. What you can do for free is everything around it:
- The Mailfois free tools. A pre-send checker that scores subject, preheader, links, deliverability and accessibility; a spam checker; an inbox preview of how your from name, subject and preheader sit in the inbox list (not a render of the email itself); and a plain-text generator. No sign-up, and they run in your browser.
- mail-tester. Send your email to a test address and get a spam score with SPF, DKIM and DMARC checks. Occasional manual tests don't need an account; subscriptions start at $10 a month for 50 tests.
- Parcel's Community plan. Free for one person writing email code, with HTML problem checking, previews in the editor and accessibility testing.
- Your own test sends. Unfashionable, but a test send to a few real accounts on the clients your audience actually uses catches a lot. Check your ESP's reporting for which clients those are.
If you need review and approval too
This is the most common gap. Email on Acid gets the email right; something else has to get it agreed.
- Litmus combines rendering, review and approvals, and analytics, from one vendor. Litmus is now part of Validity Engage and doesn't publish prices; Capterra lists its entry Core plan at $500 a month for five users. See our Litmus alternatives comparison for more.
- Parcel Business adds approvals and feedback to Parcel's editor, at $56 per user a month, with inbox previews as a paid add-on.
- Mailfois handles review and approval without rendering: versioned review rounds, sign-off limited to named approvers, rules-based brand checks before approval and a library of everything sent. It also does the campaign plan, with each market's progress tracked separately. The Team plan is £24 per seat a month at the founder price, minimum three seats.
Keeping Email on Acid for rendering and adding an approval tool is often cheaper than moving everything to one vendor. Email on Acid Basic plus three Mailfois Team seats is $186 a month before tax, against Litmus Core's listed $500.
If you code your own emails
Parcel is built for this. It's a code editor that understands email, with snippets, HTML problem checking and test sends. Pro is $29 per user a month, and inbox previews in more than 80 real inboxes are an add-on from $49 for 500 previews. If your team builds in your ESP's drag-and-drop editor, it's the wrong tool.
If your worry is the spam folder, not the layout
A perfect render is no use in the junk folder. If deliverability is the real concern, start with your authentication: SPF, DKIM and DMARC set up correctly on your sending domain. mail-tester gives a quick spam score per email. Your ESP's own reports on bounces, complaints and inbox providers tell you more than any pre-send test can. Rendering tools, Email on Acid included, are a pre-send check and not a deliverability programme.
Other rendering tools
- Testi@ is a screenshot preview tool registered in London, with a spam test, side-by-side comparison and shareable links. Check its site for current prices.
- Mailtrap is a sandbox for developers testing transactional and product email, with a free plan and paid plans from $17 a month. Device previews are available on request as an add-on.
At a glance
| If you want | Look at | Watch out for |
|---|---|---|
| The same job for free | Free pre-send tools, mail-tester, Parcel Community, real test sends | None of them render across 100+ clients |
| Rendering plus approvals in one product | Litmus | No published prices; listed at $500/month for 5 users |
| Approvals and planning next to your testing tool | Mailfois, alongside Email on Acid | Mailfois doesn't render emails |
| An editor for hand-coded email | Parcel | Inbox previews are a paid add-on |
| Testing transactional email in development | Mailtrap | Not built for marketing campaigns |
Our honest take
If rendering is the job, Email on Acid is hard to beat on price, and unlimited users is genuinely useful. Most teams looking for an alternative don't need to replace it. They need to fill the gap next to it, usually approvals, and sometimes planning across markets. If you're on a tight budget and only test occasionally, the free tools above plus careful test sends will get you a long way.
Sources, checked October 2026: emailonacid.com, Email on Acid pricing, Capterra Litmus pricing, Parcel pricing, Mailtrap pricing, mail-tester pricing, testi.at. Spotted something out of date? Tell us and we'll fix it.
