Use Haraka only for outbound

[Xumeiquer]

Is there a way to use Haraka only to outbound emails? Something like I leave a eml on a particular folder and Haraka pick it up, validate, and sends it out.

[RagedPanda]

There's no built-in "pickup folder" like IIS/Exchange have, but Haraka is perfectly fine as an outbound-only relay. Pretty much anything that gets marked as relaying goes into the outbound queue and Haraka delivers it via MX. Two ways to feed it:

1. Submit over SMTP from a small script (easiest). Turn on the relay plugin (add relay to config/plugins) and allow localhost in config/relay_acl_allow:

127.0.0.1/32

The ACL check is on by default in the relay plugin. Then whatever drops the .eml files can just send them to Haraka, e.g. with nodemailer:

const nodemailer = require("nodemailer");
const fs = require("node:fs");

const transport = nodemailer.createTransport({ host: "127.0.0.1", port: 25 });

await transport.sendMail({
  envelope: { from: "noreply@example.com", to: ["user@example.org"] },
  raw: fs.readFileSync("/path/to/outbox/msg.eml"),
});

If it's not on the same box, use port 587 with the auth/flat_file plugin instead of an IP ACL.

2. Do it inside Haraka with a plugin. Write a plugin that watches the folder and hands each file to the outbound queue:

const outbound = require("./outbound");

outbound.send_email(from, to, contents, (code, msg) => {
  if (code === DENY) plugin.logerror(`queue failed: ${msg}`);
});

The callback fires when it's queued, not delivered, so hook delivered / bounce if you want to know the outcome. You'd also need to take the envelope from/to from somewhere, either parse the headers or keep a small sidecar file.

Personally I'd go with 1, since you get the normal SMTP path (DKIM signing via dkim, limits, logging) for free and the folder watcher stays dead simple. For the "validate" part you can add whatever checks you want in a data_post plugin, and they'll run on relayed mail too.