@incsub/emdash-sendmail

Built and maintained by WPMU DEV.

An email transport plugin for EmDash CMS, scoped to WPMU DEV Hosting. Routes outgoing mail through the local sendmail binary; the host's MTA rewrites sender headers and relays via MailChannels. Zero configuration — install, rebuild, done.

If WordPress emails work on your WPMU DEV server, EmDash emails work the same way after installing this plugin.

Verified in production: Real round-trip on emdash@0.11.1 delivered with SPF pass, DKIM pass, DMARC pass (p=REJECT, strict alignment) via MailChannels into Gmail. No deliverability blemishes.

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Why this plugin exists

EmDash ships an email pipeline but no production transport. Out of the box, calls to ctx.email.send(...) throw EmailNotConfiguredError, and magic-link / invite / signup flows silently degrade. This plugin fills the gap with the simplest possible transport that works on WPMU DEV's stack.

What it does

• Registers as the active EmDash email transport via the email:deliver exclusive hook
• Hands every outgoing message to /usr/sbin/sendmail -t via nodemailer
• Lets the WPMU DEV MTA handle sender identity, SPF/DKIM/DMARC alignment, and MailChannels relaying — none of that is configured in the plugin
• Logs every send (success and failure) through EmDash's ctx.log so issues show up in the Hub server logs

That's the whole plugin. ~40 lines of real code, one optional config field, no admin UI.

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Install

The standard WPMU DEV Hosting install flow — edit package.json on the server, then click Rebuild in the Hub.

1. SSH into your hosting and edit package.json in your EmDash site root:

     "dependencies": {
   +   "@incsub/emdash-sendmail": "github:wpmudev/emdash-sendmail#v1.0.2"
     }

2. Edit astro.config.mjs:

   import { defineConfig } from "astro/config";
   import emdash from "emdash/astro";
   import { sqlite } from "emdash/db";
   import { sendmailPlugin } from "@incsub/emdash-sendmail";
   
   export default defineConfig({
     output: "server",
     integrations: [
       emdash({
         database: sqlite({ url: "file:./data.db" }),
         plugins: [sendmailPlugin()],
       }),
     ],
   });

3. Click Rebuild in the WPMU DEV Hub. This runs npm install + npm run build + restart with the right permissions.

4. That's it. EmDash auto-selects the plugin as the active email transport (it's the only one installed), so no further admin action is needed. Send a test from Admin → Settings → Email to verify.

Local development

npm install github:wpmudev/emdash-sendmail#v1.0.2

Then wire into astro.config.mjs and restart npx emdash dev. For development against an in-progress copy of the plugin:

npm install file:../path/to/emdash-sendmail

Local-path installs only need a small Vite hint to dedupe the symlinked dependencies. Skip this if you installed from GitHub:

vite: {
  resolve: { dedupe: ["emdash", "astro"] },
  optimizeDeps: { exclude: ["@incsub/emdash-sendmail"] },
},

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Configuration

There are two optional fields. Most sites don't need either:

sendmailPlugin({
  sendmailPath: "/usr/sbin/sendmail",     // default — only set if your host puts the binary elsewhere
  messageIdDomain: "yourwpsite.email",    // default — matches the MTA's rewrite target
});

You won't need to set anything. Sender identity (From: / envelope sender / Sender: / SPF / DKIM / DMARC) is handled entirely by the WPMU DEV MTA — the plugin deliberately leaves all of it alone so the host can do its job. The plugin generates Message-ID: headers locally so they align with the MTA-rewritten From: (no @localhost fallback).

What about the From: address? WPMU DEV's Postfix rewrite rule *@* noreply@yourwpsite.email Ffs rewrites three things on every outgoing message: the visible From: header, the envelope sender, and the Sender: header. All outgoing mail will show as coming from noreply@yourwpsite.email, regardless of anything the plugin does. This is by design — it guarantees SPF / DKIM alignment with the relay. If you need a different sender address, ask your hosting support; it isn't something the plugin can override.

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How sends flow

caller (auth, invite, plugin, admin test-send)
   │
   ▼  ctx.email.send({ to, subject, text, html? })
EmailPipeline (EmDash core)
   │  ├─ email:beforeSend hooks (other plugins can transform / cancel)
   │  ▼
   │  email:deliver  ◀── this plugin (exclusive)
   │     │
   │     └─ /usr/sbin/sendmail -t  →  Postfix (rewrites headers)  →  MailChannels  →  recipient
   │
   └─ email:afterSend hooks (other plugins can log / retry / fire webhooks)

EmDash's email:beforeSend and email:afterSend hooks remain available for layered behaviour from other plugins; this plugin only claims the email:deliver slot.

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Verifying it works

After install + Rebuild:

1. Go to Admin → Settings → Email. The active provider should show as hosting-email.
2. Send a test email from that page. It should arrive within seconds with From: noreply@yourwpsite.email.
3. Tail the Hub server logs while sending — you'll see one [hosting-email] delivered ... entry per send.

Troubleshooting

If sends fail, the Hub logs will show one [hosting-email] delivery FAILED ... line per attempt with the underlying nodemailer error code. The two failures you might realistically see on WPMU DEV Hosting:

Code	What it means	What to do
ENOENT	/usr/sbin/sendmail not at that path	Set sendmailPath in plugin options to the actual location; ask hosting support if unsure
EACCES	Node process can't exec sendmail	Contact WPMU DEV support — this shouldn't happen on standard hosting

Anything else (relay rejections, message-deferred warnings, etc.) is happening downstream of the plugin and is a hosting / MTA / MailChannels matter.

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Limitations

1. WPMU DEV Hosting only. The defaults assume the host MTA rewrites sender headers. On other hosts, mail will go out with no From: header and most relays will reject it. Forks are welcome — see src/sandbox-entry.ts.
2. Single transport at a time. EmDash's email:deliver is exclusive — only one provider plugin can be active. Don't enable this alongside another email plugin.
3. No retry / queue. Failed sends throw to the caller. Pair with a separate email:afterSend retry plugin if you need durability.
4. Native plugin only. Uses nodemailer + Node child_process; can't run in EmDash's sandboxed V8 isolate runtime.

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Developing the plugin

git clone https://github.com/wpmudev/emdash-sendmail.git
cd emdash-sendmail
npm install

Make your changes in src/. Then build before committing or testing in a consumer site:

npm run build       # regenerates dist/
npm run typecheck   # optional: confirms TS is clean

The compiled dist/ is committed to git so GitHub installs work without needing the consumer's host to run a build step. If you change src/ without rebuilding, your changes won't reach consumers until you do npm run build and commit dist/.

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Made by

WPMU DEV — managed hosting and WordPress tooling used by 100k+ agencies. This plugin is part of our exploration of EmDash CMS. Questions, bug reports, or feature requests welcome at github.com/wpmudev/emdash-sendmail/issues.

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License

MIT — see LICENSE.