All comparisons
vs MailSlurpEmail testing4 min read
MailSlurp vs Mails.ai — test email volume, codes and the MCP server compared
www.mailslurp.comMailSlurp is a large email and SMS testing platform. Mails.ai does one part of that job: it catches the emails your app sends during a test and reads the code or link inside. If that part is all you need, the difference is how much mail you get for the money.
The same job, at different volumes
Both give a test an address, wait for the email your app sends to it, and return the sign-up code or magic link. Both work from Claude Code through a hosted MCP server. The plans are where they part:
- Free: Mails.ai takes 3,000 inbound replies a month. MailSlurp’s free plan takes 500 received emails.
- About $20: Mails.ai Pro takes 50,000 a month. MailSlurp Starter, at $19.99, takes 1,000.
- The next step up: Mails.ai Scale, at $99, takes 500,000. MailSlurp Pro, at $49.99, takes 5,000.
A suite that signs up a new user in every run gets through 1,000 emails quickly: 50 runs a day of a one-email test is about 1,500 a month.
Where MailSlurp leads
- Breadth. SMS testing with phone numbers, previews on real mail clients and devices, inbox placement tests, email audits and warm-up. Mails.ai has none of these.
- Languages. Eleven SDKs, including Java, C#, Ruby, Go, Kotlin, Swift and Dart, and guides for Selenium, WebdriverIO, Pytest, JUnit and more. Mails.ai has TypeScript and Python SDKs, a CLI and a REST API.
- Track record. MailSlurp is established; its npm client is downloaded about 850,000 times a month. Mails.ai is live and self-serve with a small, early customer base.
Which to choose
- Choose MailSlurp if your tests need SMS, device previews or placement tests, or a native SDK in a language other than TypeScript or Python.
- Choose Mails.ai if your tests only need email codes and links and you run them often enough that 500 or 1,000 emails a month will not last.
The email-testing guide shows a Playwright and a Cypress test that sign up with a plus address, wait for the email and read the code.
Side-by-side
MailSlurp vs Mails.ai — feature matrix
| Dimension | Mails.ai | MailSlurp |
|---|---|---|
| Free plan | ✓3,000 emails and 3,000 inbound replies a month, 20 new plus addresses a day | 500 emails received a month, 100 new inboxes a month |
| About $20 a month | ✓Pro, $20: 50,000 inbound replies a month | Starter, $19.99: 1,000 emails received a month |
| The next plan up | Scale, $99: 500,000 inbound replies a month | Pro, $49.99: 5,000 emails received a month |
| Sign-up codes and magic links | ✓codes and links on every received message | ✓OTP and MFA testing that captures codes |
| Waiting for the email | ✓One call that waits up to 50 seconds | ✓Waits for messages, with its own guide |
| MCP server for Claude Code and other agents | ✓Hosted or via npx, with a wait tool; plus a Claude Code plugin | ✓Hosted, with tools that list, search and wait for email |
| SDK languages | TypeScript and Python, plus a CLI and REST | ✓Eleven, from Java and C# to Swift and Dart |
| Test frameworks | Cypress plugin and Playwright fixture; any runner through the SDKs | ✓Guides for Playwright, Cypress, Selenium, WebdriverIO, Pytest, JUnit and more |
| SMS testing | —Not offered | ✓Phone numbers, from its $49.99 plan |
| Device previews, inbox placement tests, email audits | —Not offered | ✓All three, with monthly allowances by plan |
FAQ
Questions readers ask after this page
Why does Mails.ai take so much more test mail for the money?
Mails.ai sells one job: receiving your app’s emails and reading the code or link inside. Free takes 3,000 inbound replies a month, Pro ($20) 50,000 and Scale ($99) 500,000. MailSlurp’s plans also pay for SMS, device previews, inbox placement tests, audits and warm-up, and they take 500, 1,000 ($19.99) and 5,000 ($49.99) received emails a month.
Does Mails.ai create a new inbox for every test?
It does not need to. Each test uses its own plus address on one agent, such as qa.acme+run-1842@in.mails.ai, and waits for mail sent to exactly that address. Free takes mail at 20 new plus addresses a day, Pro at 1,000 and Scale at 10,000; an address that already received mail that day keeps receiving it.
Can I use it from Claude Code, like MailSlurp’s MCP server?
Yes. Both have a hosted MCP server. Mails.ai’s also runs locally through npx and comes in a Claude Code plugin; its wait tool returns the newest matching email, waiting up to 50 seconds. See /docs/mcp.
When is MailSlurp the better choice?
When your tests read SMS codes, you need previews on real mail clients or inbox placement tests, or your suite is in a language Mails.ai has no SDK for, such as Java, C#, Ruby, Go or Swift. Mails.ai’s REST API works from any language, but MailSlurp gives you a native client.
Will codes from Google, Apple or my bank arrive?
No. A sign-in code or a verify, sign-in or password-reset link from a service such as Google, Microsoft’s account team, Apple, a payment app or a bank never reaches a plus address; only a record is kept. Mail from your own app arrives.
Related
What to read next
Catch your first test email
Free covers 3,000 inbound emails a month and 20 new test addresses a day, with no card. Upgrade when your suite outgrows it.
Get your API key