mailtrap-testing-with-sandbox
Lets your agent capture outgoing emails for testing. It's useful for developers to check how emails look, perform spam checks, and test fake inboxes.
What it does
This tool lets you send test emails without them reaching real recipients. It's like having a test inbox to check if your emails are being sent correctly.
When to use it
- ✓When developing a website or app and wanting to test outgoing emails.
- ✓To check the appearance and content of an email before sending it to customers.
- ✓In automated tests to ensure emails function as expected.
Example of what to ask your AI
“Set up sending test emails to my test inbox in Mailtrap.”
Want more? Open the sections below.
How to use
The easiest way: copy the message below and paste it into Claude, ChatGPT, Cursor or any AI. It reads the skill and follows the instructions.
Skill link
Ready-to-paste message
How it works
You configure your system to send emails to a special Mailtrap address instead of the real recipient's address. This way, the emails are stored in Mailtrap for you to inspect.
Installation
Easiest way: copy the skill link and paste it into Claude, ChatGPT or Cursor asking it to follow the instructions.
In the terminal (Claude Code, Codex, Cursor), in your project folder:
npx skills add sickn33/agentic-awesome-skills --skill mailtrap-testing-with-sandboxOr download just the file:
curl -L https://raw.githubusercontent.com/sickn33/agentic-awesome-skills/main/plugins/agentic-awesome-skills-claude/skills/mailtrap-testing-with-sandbox/SKILL.md -o SKILL.mdTechnical content (original SKILL.md)
Original text by the author, straight from GitHub.
Testing with Mailtrap Email Sandbox
Overview
Email Sandbox captures mail in sandboxes (test inboxes)—a test environment where messages are not delivered to real recipients. You can send to sandboxes using our SDKs, HTTP API, or SMTP, depending on your needs.
Before generating SDK code: read the README of the relevant SDK repository (see mailtrap-sending-emails) for current sandbox mode options, inbox id, and constructor flags. Do not rely on memory.
Related skills: mailtrap-sending-emails (live sending hosts and streams).
When to use
- You want no real delivery: dev, staging, CI, or demos where mail must stay in a test inbox.
- You need to inspect what was sent: bodies, headers, attachments, or basic checks (e.g. spam report) via Sandbox / Testing API or the UI.
- You are automating tests against captured mail.
- You will only change SMTP settings so an existing app sends into a sandbox—no need for a framework-by-framework tutorial from this skill.
When not to use
- Live sends to real recipients (
mailtrap-sending-emails). - For full framework setup guides or detailed API references, link users to Mailtrap's Integration tab for SMTP/API details and the API docs for specifics—don't cover every framework or API field here.
Quick reference
API base
| Service | Send mail URL | Auth header examples |
|---|---|---|
| Email Testing API (REST) | https://sandbox.api.mailtrap.io/api/send/{inbox_id} |
Authorization: Bearer $MAILTRAP_SANDBOX_API_TOKEN |
Tokens and account_id
Sandbox uses a separate token ($MAILTRAP_SANDBOX_API_TOKEN, Testing/Sandbox scope) — never reuse the live $MAILTRAP_API_TOKEN. The account_id in the example endpoints below is resolved at runtime via GET https://mailtrap.io/api/accounts. Store tokens in environment variables or a secrets manager.
When to use API vs SMTP
Use SMTP when testing apps that already send mail via SMTP (just update the host, port, and credentials). Use the HTTP API when building new integrations or your app can make HTTP requests; it's better for programmatic testing and automation.
SMTP settings (sandbox)
| Setting | Value |
|---|---|
| Host | sandbox.smtp.mailtrap.io |
| Ports | 2525 (default), 25, 465 (SSL), 587 |
| Username / Password | Per sandbox credentials from the Integration tab in the Mailtrap UI |
Never use sandbox credentials or endpoints in production. Messages will only be captured in the sandbox, not delivered.
Key parameters
- Inbox ID: Every sandbox (test inbox) has a unique inbox id, visible in the UI URL and needed for sending or REST API operations.
- Token scope: Use a token with permissions for the relevant project and test inbox.
Typical use cases
- Capture all outbound mail in dev, test, or staging (no real recipients).
- View, validate, and assert message headers, bodies, HTML, attachments, or spam score.
- Run integration or CI checks that read from the Email Sandbox API.
- Test Mailtrap templates by pointing API or SDK/SMTP at
sandbox.api.mailtrap.io/sandbox.smtp.mailtrap.iowith a valid inbox id.
Example API paths
Use API docs for details, but typical endpoints include:
| Operation | URL | Reference |
|---|---|---|
| List sandboxes | GET https://mailtrap.io/api/accounts/$MAILTRAP_ACCOUNT_ID/inboxes |
Sandboxes API |
…
FAQ
Do I need a Mailtrap account?
Yes, you need a Mailtrap account to use the test inbox.
Can I send emails to real people with this?
No, this tool is only for testing. Emails are not delivered to real recipients.
How do I see the emails that were sent for testing?
You can view the emails directly in the Mailtrap interface, where they are stored.
Details
Original description by the author
Capture outbound email in Mailtrap Email Sandbox for development, staging, CI, HTML inspection, spam checks, and fake inbox tests.
Popularity
- GitHub stars
- 48k
- Ranking position
- #3522
- License
- MIT
- Updated
- 10/15/2026
Comments
- …
More skills from this repository
00-andruia-consultant
Helps your agent start or improve AI projects. It analyzes code, suggests tools, and creates action plans in Spanish.
sickn33/agentic-awesome-skills
007
Lets your agent perform security audits and threat modeling. It's useful for protecting projects against attacks and vulnerabilities.
sickn33/agentic-awesome-skills
10-andruia-skill-smith
Helps your agent create or improve AI tools. It defines how tools work, writes documentation, and validates the structure.
sickn33/agentic-awesome-skills
20-andruia-niche-intelligence
Lets your agent create a summary about a specific industry. It's useful for understanding the context, rules, usage patterns, and risks of a project, using reliable sources.
sickn33/agentic-awesome-skills
Similar skills
api-connector-builder
Has your agent build new API connections following the existing pattern. Use when you need to add one more integration without creating a new way of doing things.
affaan-m/ECC
api-design
Helps your agent design REST APIs following best practices. It's useful for defining how APIs communicate, how errors are shown, and how to organize data.
affaan-m/ECC
backend-patterns
Helps your agent with server-side architecture patterns and database optimization. It's useful for building or reviewing code that runs on the server.
affaan-m/ECC