docs: add dupontbertrand:mail-preview to community packages

Add documentation page for the mail-preview package, a zero-config
dev-mode email preview UI that captures outgoing emails and displays
them at /__meteor_mail__/.

Ref: https://forums.meteor.com/t/built-in-mail-preview-ui-for-dev-mode/64489

v3-docs/docs/.vitepress/config.mts

@@ -461,6 +461,10 @@ export default defineConfig({
                 text: "jam:offline",
                 link: "/community-packages/offline",
               },
+              {
+                text: "dupontbertrand:mail-preview",
+                link: "/community-packages/mail-preview",
+              },
             ],
             collapsed: true,
           },

v3-docs/docs/community-packages/index.md

@@ -40,6 +40,10 @@ Please bear in mind if you are adding a package to this list, try providing as m
 - [`jam:soft-delete`](./soft-delete.md), An easy way to add soft deletes to your Meteor app
 - [`jam:archive`](./archive.md),
 
+#### Developer tools
+
+- [`dupontbertrand:mail-preview`](./mail-preview.md), Zero-config dev-mode mail preview UI — view captured emails at `/__meteor_mail__/`
+
 #### Utilities
 
 - [`jam:offline`](./offline.md), An easy way to give your Meteor app offline capabilities and make it feel instant

v3-docs/docs/community-packages/mail-preview.md

@@ -0,0 +1,123 @@
+# Mail Preview
+
+- `Who maintains the package` – [Bertrand Dupont](https://github.com/dupontbertrand)
+
+[[toc]]
+
+## What Is It?
+
+A zero-config, dev-mode mail preview UI for Meteor. Every email sent via `Email.sendAsync()` is captured and displayed in a browser UI at `/__meteor_mail__/`.
+
+Inspired by similar features in Rails (Action Mailer Preview), Phoenix (Swoosh), Laravel (Mailtrap), and Django (console backend).
+
+This is a `devOnly` package — it is **automatically excluded from production builds**. Zero overhead in production, no need to remove it before deploying.
+
+## How to Download It?
+
+```bash
+meteor add dupontbertrand:mail-preview
+```
+
+That's it. No configuration needed.
+
+## How to Use It?
+
+1. Start your Meteor app in development mode (`meteor run`)
+2. Trigger any email — password reset, verification, enrollment, or your own `Email.sendAsync()` calls
+3. Open `http://localhost:3000/__meteor_mail__/` in your browser
+
+### What You Get
+
+- **Mail list** — live-updating list of all captured emails (polls every 2s, no page reload)
+- **Mail detail** — view each email with tabs for **HTML render**, **Plain Text**, and **HTML Source**
+- **Clickable links** — verification, password reset, and enrollment links work directly from the preview
+- **JSON API** — programmatic access for testing and tooling
+- **Clear all** — one-click button to clear captured mails
+
+### Example: Capturing an Accounts Email
+
+```js
+// Server — nothing special needed, just use Meteor's built-in accounts
+import { Accounts } from 'meteor/accounts-base';
+
+// When a user registers, Meteor sends a verification email.
+// mail-preview captures it automatically.
+Accounts.sendVerificationEmail(userId);
+```
+
+Then open `/__meteor_mail__/` to see the captured email, click the verification link, and it works.
+
+### Example: Custom Emails with MJML
+
+```js
+// Server
+import { Email } from 'meteor/email';
+import mjml2html from 'mjml';
+
+const { html } = mjml2html(`
+  <mjml>
+    <mj-body>
+      <mj-section>
+        <mj-column>
+          <mj-text font-size="20px" color="#333">Hello from Meteor!</mj-text>
+          <mj-button background-color="#0d6efd" href="https://meteor.com">
+            Visit Meteor
+          </mj-button>
+        </mj-column>
+      </mj-section>
+    </mj-body>
+  </mjml>
+`);
+
+await Email.sendAsync({
+  from: 'noreply@example.com',
+  to: 'user@example.com',
+  subject: 'Welcome!',
+  html,
+});
+```
+
+The MJML-rendered email is captured and displayed with full HTML rendering in the preview UI.
+
+## JSON API
+
+For programmatic access (useful in tests or tooling):
+
+| Method   | Endpoint                       | Description              |
+| -------- | ------------------------------ | ------------------------ |
+| `GET`    | `/__meteor_mail__/api/mails`      | List all captured mails  |
+| `GET`    | `/__meteor_mail__/api/mails/:id`  | Get a single mail        |
+| `DELETE` | `/__meteor_mail__/api/mails`      | Clear all captured mails |
+
+### Example: Using the API in Tests
+
+```js
+// In a test, after triggering an email:
+const res = await fetch('http://localhost:3000/__meteor_mail__/api/mails');
+const { mails } = await res.json();
+
+assert.equal(mails[0].subject, 'Verify your email');
+assert.ok(mails[0].text.includes('verify-email'));
+```
+
+## How It Works
+
+The package uses `Email.hookSend()` to intercept outgoing emails and store them in memory (up to 50 — oldest are evicted). A middleware mounted via `WebApp.rawConnectHandlers` serves the preview UI.
+
+- **Dev mode only** — guarded by `Meteor.isDevelopment` and `devOnly: true` in `package.js`
+- **No SMTP needed** — emails are captured before they reach any transport
+- **No external dependencies** — uses only Meteor core packages (`email`, `webapp`, `ecmascript`)
+- **Works alongside `MAIL_URL`** — if set, emails are still sent normally; the hook captures a copy
+
+## Compatibility
+
+- Meteor 3.4+
+- Works with `accounts-password` emails (verification, reset password, enrollment)
+- Works with custom `Email.sendAsync()` / `Email.send()` calls
+- Compatible with Rspack bundler
+
+## Sources
+
+- **Atmosphere:** [dupontbertrand:mail-preview](https://atmospherejs.com/dupontbertrand/mail-preview)
+- **GitHub:** [dupontbertrand/meteor-mail-preview](https://github.com/dupontbertrand/meteor-mail-preview)
+- **Forum Discussion:** [Built-in Mail Preview UI for Dev Mode](https://forums.meteor.com/t/built-in-mail-preview-ui-for-dev-mode/64489)