resend-box

Original：🇺🇸 English
Translated

Resend Box is a local email sandbox that mocks the Resend API and captures emails for inspection. Use this skill when working with the Resend SDK or SMTP to send emails during development. It captures all emails sent via the Resend SDK (when RESEND_BASE_URL points to the sandbox) or via SMTP (port 1025). Use to verify emails are sent correctly, inspect email content, or test email templates without sending real emails.

6installs
Sourcetomaspozo/resend-box
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NPX Install

npx skill4agent add tomaspozo/resend-box resend-box

Tags

Translated version includes tags in frontmatter
resend-boxemail-sandboxsmtp-testinglocal-developmentemail-template-testing

SKILL.md Content

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Resend Box Skill

Resend Box is a local email sandbox that:
  1. Mocks the Resend API - Drop-in replacement for 
    https://api.resend.com
  2. Runs an SMTP server - Captures emails sent via SMTP on port 1025
  3. Provides a Web UI - View captured emails at http://127.0.0.1:4657
  4. Stores emails in-memory - All emails are lost when the server restarts

When to Use

  • You're using the Resend SDK and want to test emails locally
  • You're sending emails via SMTP and need to verify they're sent correctly
  • You want to inspect email content (HTML, text, headers) during development
  • You need to verify emails are sent to the correct recipients
  • You're testing email templates before sending to real users

Prerequisites

Start Resend Box:
bash
npx resend-box start
Configure your project to use the sandbox - see Setup Guide.

Quick Reference

Send an Email (via Resend API)

bash
curl -X POST http://127.0.0.1:4657/emails \
  -H "Content-Type: application/json" \
  -d '{
    "from": "sender@example.com",
    "to": "recipient@example.com",
    "subject": "Test Email",
    "html": "<p>Hello!</p>"
  }'
Required fields: 
from
, 
to
, 
subject
Optional fields: 
html
, 
text
, 
cc
, 
bcc
, 
replyTo

Get All Emails

bash
curl http://127.0.0.1:4657/sandbox/emails

Filter Emails by Recipient

bash
curl "http://127.0.0.1:4657/sandbox/emails?to=user@example.com"
The 
to
filter is case-insensitive and supports partial matching.

Get a Specific Email

bash
curl http://127.0.0.1:4657/sandbox/emails/{id}

Delete All Emails

bash
curl -X DELETE http://127.0.0.1:4657/sandbox/emails

View in Browser

Open http://127.0.0.1:4657 to view captured emails in the web UI.

Detailed Documentation

  • Setup Guide - Configure your project to use Resend Box
  • Send Email Reference - Complete API for sending emails
  • Get Emails Reference - Complete API for retrieving and filtering emails