Initial commit

index.js

@@ -0,0 +1,68 @@
+/*
+    SMTP Proxy
+    Author: Alex Rennie-Lis
+    Description: Presents an unauthenticated SMTP server for local legacy devices, and 
+        proxies traffic to a defined relay host
+    Version: 1.0.0
+*/
+
+const SMTPServer = require("smtp-server").SMTPServer;
+const nodemailer = require("nodemailer");
+
+if (
+    !process.env.RELAY_HOST || 
+    !process.env.RELAY_PORT
+) {
+    console.log ("Missing configuration.");
+    process.exit (1);
+}
+
+const transporter = nodemailer.createTransport({
+    host: process.env.RELAY_HOST,
+    port: parseInt(process.env.RELAY_PORT) || 465,
+    secure: process.env.RELAY_PORT === "465",
+    auth: {
+        user: process.env.RELAY_USER,
+        pass: process.env.RELAY_PASS
+    },
+    // VERBOSE DEBUGGING
+    logger: false,
+    debug: false 
+});
+
+// Verify the connection on startup
+transporter.verify((error, success) => {
+    if (error) {
+        console.error("Transporter Config Error:", error);
+    }
+    else {
+        console.log("Upstream relay is ready.");
+    }
+});
+
+const server = new SMTPServer({
+    authOptional: true,
+    onData(stream, session, callback) {
+        console.log ("Relaying message...");
+
+        const envelope = {
+            from: session.envelope.mailFrom.address,
+            to: session.envelope.rcptTo.map(r => r.address)
+        };
+        
+        transporter.sendMail ({envelope: envelope, raw: stream}, (err, info) => {
+            if (err) {
+                console.error ("Relay Error:", err.message);
+                return callback (new Error ("Relay failed!"));
+            }
+            console.log("Relay success:", info.messageId);
+            callback();
+        });
+    }
+});
+
+const listenPort = process.env.SMTP_PORT || 2525; // Default to port 2525
+
+server.listen (listenPort, '0.0.0.0', () => {
+    console.log (`Relay active: Port ${listenPort} -> ${process.env.RELAY_HOST}:${process.env.RELAY_PORT}`);
+});