Email on Acid vs Mail-Tester (2026): which should you pick?
As of Nov 13, 2026, Mail-Tester grades higher than Email on Acid: 2.8 against 1.8 out of 4.0.
Checked Nov 12, 2026 and Nov 13, 2026 · graded Nov 12, 2026 and Nov 13, 2026 by ToolGPA
Mail-Tester grades higher on value for money, the free plan and ease of use. They get the same grade on features and platforms.
Price, platforms and features side by side. The table says where each price was read and when.
Email on Acid
Email previews and pre-send QA, now moving to Mailgun Inspect
Mail-Tester
Send an email to a test address and get a spam score out of 10
Which one is for you
Pick Email on Acid if
- Fits if you check each campaign across many email clients
- Works for agencies that need unlimited users on one account
Look elsewhere if
- Pricey if you add it up, at $99 a month for 1,000 previews
- Skip it if you want accessibility or spam checks on the cheap plan, as they start at Premium, $199
- Watch out: the pricing page says customers move to Mailgun Inspect from June 2026 and old tests are not carried over
- Watch out: it does not send email, so you need a separate sending service
- Watch out: the trial length is not stated
Pick Mail-Tester if
- Fits if you want to check one newsletter or template before sending
- Works for developers who want the score inside their own tool
Look elsewhere if
- Tight if you test more than 3 times a day on free, with results kept for 7 days
- Skip it if you want ongoing monitoring, since it tests one message at a time
- Watch out: the score comes from SpamAssassin and other spam filters differ
- Watch out: prices exclude VAT
How we grade them
| 1.8GPAEmail on AcidWeak | 2.8GPAMail-TesterGood | |
|---|---|---|
| Value for money | DBasic is $99 a month for 1,000 previews, above the category's dearer quarter ($49). The checks most people want sit on Premium at $199. | BSubscriptions start at $10 a month for 50 tests, level with the $10 cheaper quarter of deliverability tools. A 10-test pack is $5, and prices exclude VAT. |
| Free plan and trial | DA free trial is offered, but the page states no length. | B3 tests in any 24 hours with no account, results kept for 7 days. One person checking now and then can live on that. |
| Features | CPreviews, accessibility, link and image checks and spam analysis. It does not send email. | CA spam score, a configuration report and a JSON API. It uses a stock SpamAssassin setup, so a perfect score does not guarantee inbox placement, and it does one message at a time. It does that job fully, and it is a smaller job. |
| Ease of use | CNo rating on record. Paste or send the email and read the results, with a migration to Mailgun Inspect under way. | BNo store rating on record. You send a mail to a displayed address and read the result, so there is nothing to set up. |
| Platforms and integrations | BWeb, with an API and unlimited users on every plan and one listed integration. | BWeb only, with a JSON API, an iframe and white-labeling. No desktop or phone app. |
| Best for | previewing an email in many clients before a send | checking one email's spam score |
The GPA is the average of the five grades: an A is 4 points, an F is none. The full reasons are on each tool's page: Email on Acid and Mail-Tester. How we grade
Price against what you get
Email on Acid starts at $99 a month and scores 2.3 out of 4 on features, ease of use and platforms. Mail-Tester starts at $10 a month and scores 2.7.
Mail-Tester scores higher and starts $89 a month lower. Of the other email verification and deliverability tools on the chart, 8 score higher than Email on Acid for less, and none scores higher than Mail-Tester for less.
Features, ease of use and platforms, averaged
What paid plans start at, a month (each step along is roughly double) →
- The best score at each price
- Has a free plan
- No free plan
Where they differ
- Email on Acid also covers email campaigns.
At a glance
| Email on Acid | Mail-Tester | |
|---|---|---|
| Pricing | Free trial | Free plan |
| Starts at | $99 per month | $10 per month for 50 tests; or $5 once for 10 tests |
| Free plan | None | Free web interface: 3 tests per 24 hours, results kept for 7 days. |
| Free trial | Free trial offered; its length is not stated on the page | None listed |
| Web | ||
| Made by | Email on Acid | Mail Tester LLC |
| Price read from | emailonacid.com | mail-tester.com |
| Checked | Nov 13, 2026 | Nov 12, 2026 |
Worth knowing
Email on Acid
- The pricing page says current customers will move to Mailgun Inspect from June 2026, and that old previews and tests are not carried over.
- Annual-plan customers migrate at the end of their current term.
- Basic has no accessibility, spam or link checks; those start at Premium.
- It does not send email; the FAQ says you need a separate sending service.
Mail-Tester
- Scores come from a stock SpamAssassin setup; the FAQ says other spam filters differ, so a perfect score does not guarantee inbox placement.
- The free version allows 3 tests in 24 hours and keeps results for 7 days; an account with your own prefix keeps them 30 days.
- Prices exclude VAT.
- It tests one message at a time and does not monitor sending over time.
Key features
Email on Acid
- Client and device previews
- Each screenshot of a client or device counts as one preview, so a test across 50 clients uses 50 previews.
- Accessibility checks
- Premium tests are based on the W3C Web Content Accessibility Guidelines, which the vendor ties to the European Accessibility Act.
- Link and image validation
- Premium checks links and images in a message. The FAQ says these checks, unlike previews, are unlimited.
- Spam content analysis
- Premium includes content spam checks and HTML code analysis, judged on the message itself and not on your sending reputation.
- API access and unlimited users
- Every plan includes API access, and none of the plans limit how many people on a team can use the account.
Mail-Tester
- Spam score
- Scores a sent message out of 10 using a default SpamAssassin install, with the sign reversed so that a higher score is better.
- Configuration report
- Reviews the message, the mail server and the sending IP, and lists what is set up correctly and what is not.
- JSON API and iframe
- Paid plans let you embed mail-tester results in your own software.
- White-labeling and custom CSS
- Accounts can restyle the result page and fully white-label it, after contacting the company to authorize their domain.
- Usage statistics and history
- Daily, weekly and monthly usage statistics and a list of the last 30 days of tests, with no ads on results.
Plans
Email on Acid
Basic$99
per month for 1,000 previews
Unlimited users, 100+ preview clients and devices, API access; extra previews cost $0.15 each.
Premium$199
per month for 2,000 previews
Adds accessibility tests, HTML code analysis, link and image validation and spam content checks.
ContractCustom
Custom preview allotment with the Premium feature set and phone and chat support; sold through sales.
Mail-Tester
Free web interface$0
3 tests in any 24 hours, no account needed, results available for 7 days.
10 Tests$5
one-time
A pack of 10 extra tests at $0.50 each. Larger one-time packs run up to 15,000 tests for $700.
50 Tests / Month$10
per month for 50 tests
Subscription with an account; $0.20 per test.
500 Tests / Month$25
per month for 500 tests
$0.05 per test.
2,000 Tests / Month$80
per month for 2,000 tests
Marked most popular on the page; $0.04 per test.
7,500 Tests / Month$250
per month for 7,500 tests
$0.0333 per test. A 25,000-plus tier is quoted on request.
Common questions
Which is cheaper, Email on Acid or Mail-Tester?
As of Nov 13, 2026, Mail-Tester is cheaper to start with: $10 a month, against $99 a month for Email on Acid. Email on Acid starts at $99 per month, and Mail-Tester starts at $10 per month for 50 tests; or $5 once for 10 tests.
Which has a free plan, Email on Acid or Mail-Tester?
As of Nov 13, 2026, only Mail-Tester has a free plan. Email on Acid does not, though it has a free trial.
More comparisons
How this page was made
- The verdict at the top follows a fixed rule. When both tools are in the same category and either is in our top three for it, the verdict follows that ranking: the higher-placed tool is our pick. The top three weigh who each tool suits as well as its grades, so a pick can go against the GPA. Otherwise the page does not pick one and says which grades higher: the higher GPA first; on a tie, the one with a free plan, then the one that starts cheaper in dollars a month, counted the same way for both; if they are still level, what the choice depends on.
- The grades are our own, from each tool’s review or report card. The GPA is their average.
- Prices, plans and platforms come from each tool’s listing. The table above says where each price was read and when.
- The differences and the answers to the questions are worked out from those listings.