simmail vs Mailtrap
Both catch the mail your app sends so it never reaches a real person. Mailtrap is built around inspecting that mail, and also sells real sending. simmail is built around what happens next: simulated people who react and reply.
Mailtrap
Mailtrap's Email Sandbox gives your development and staging environments a fake SMTP server. Mail your app sends is captured in an inbox where you can inspect it, check its HTML against email clients and see a spam analysis. Mailtrap also has a separate product for sending real email through its API and SMTP.
simmail
simmail captures and inspects mail too, with spam scores, link checks, client compatibility and accessibility. The difference is that the addresses have people behind them. They read, ignore, click, junk, bounce and reply on their own schedule. A World sends mail in, faults can be switched on, the clock can be moved forward, and AI agents can use it over MCP. It never sends real mail.
Side by side
| Mailtrap | simmail | |
|---|---|---|
| Capture mail your app sends over SMTP | Yes | Yes |
| Send test mail with an HTTP API | Yes | Yes |
| Inspect HTML, text, raw source and headers | Yes | Yes |
| Spam score for each email | Yes | Yes |
| HTML and CSS support across email clients | Yes | Yes |
| API for automated tests | Yes | Yes |
| Read captured mail over IMAP | — | Yes |
| Sends real email to real recipients | Yes | No, never |
| Simulated recipients who open, click, junk and reply | No | Yes |
| Inbound mail that arrives on its own (leads, support, spam) | No | Yes |
| Faults such as greylisting, rate limits and bounces | — | Yes |
| A clock you can move forward | — | Yes |
| MCP endpoint for AI agents | — | Yes |
“—” means we are not sure whether Mailtrap offers it. Check Mailtrap's documentation for the current answer. Some simmail features depend on the plan; see pricing.
When Mailtrap is the better fit
- You only need to look at outgoing mail. If the job is to check that a template renders, the links are right and the spam score is fine, a capture inbox does that, and Mailtrap is a mature, widely used one.
- You need real sending. simmail cannot deliver mail to anyone, by design. If you want one provider for testing and for production sending, Mailtrap offers both.
- Your team already uses it. If Mailtrap is part of your workflow and nobody needs replies or inbound mail, there is little reason to switch.
When simmail is the better fit
- Your software depends on what recipients do. Sales sequences that stop on a reply, help desks that thread and assign inbound mail, CRMs that track opens and clicks: these need someone on the other end.
- You are building an AI email agent. An agent needs people to write to and hear back from, repeatably and safely. simmail gives it a universe of them, over MCP or the API.
- You want to test the bad days. Greylisting, rate limits, dropped connections, bounces and mail landing in Junk, on demand.
- You want to test what happens later. Follow-ups, reminders and slow replies, by moving the clock forward instead of waiting.
Using both
They do not exclude each other. Some teams may keep a capture inbox for template checks and use simmail for flows that need replies and inbound mail. Both accept mail over standard SMTP, so pointing an environment at one or the other is a configuration change.
Questions
Can simmail send my production email?
No. simmail has no relay and no outbound SMTP client. It is only for testing. Use an email sending provider, such as Mailtrap's sending product, for real mail.
Do I need to change my code to try simmail?
Usually not. Point your SMTP settings at a simmail universe, or send with the HTTP API. The quickstart walks through it.
Is this comparison up to date?
It reflects our understanding of Mailtrap at the time of writing. Products change; if something here is wrong, tell us and we will fix it.
Put real behaviour between your app and its inbox
Start free with 25 AI actions a month, no card needed. Upgrade when you need more.