smtp-server/examples/server.js

Create custom SMTP servers on the fly

/* eslint no-console: 0 */

'use strict';

// Replace '../lib/smtp-server' with 'smtp-server' when running this script outside this directory
const SMTPServer = require('../lib/smtp-server').SMTPServer;

const SERVER_PORT = 2525;
const SERVER_HOST = false;

// Connect to this example server by running
//   telnet localhost 2525
// or
//   nc -c localhost 2525

// Authenticate with this command (username is 'testuser' and password is 'testpass')
//   AUTH PLAIN dGVzdHVzZXIAdGVzdHVzZXIAdGVzdHBhc3M=

// Setup server
const server = new SMTPServer({
    // log to console
    logger: true,
    secure: true,

    // not required but nice-to-have
    banner: 'Welcome to My Awesome SMTP Server',

    // disable STARTTLS to allow authentication in clear text mode
    disabledCommands: ['AUTH', 'STARTTLS'],

    // By default only PLAIN and LOGIN are enabled
    authMethods: ['PLAIN', 'LOGIN', 'CRAM-MD5'],

    // Accept messages up to 10 MB
    size: 10 * 1024 * 1024,

    // allow overriding connection properties. Only makes sense behind proxy
    useXClient: true,

    hidePIPELINING: true,

    // use logging of proxied client data. Only makes sense behind proxy
    useXForward: true,

    // Setup authentication
    // Allow only users with username 'testuser' and password 'testpass'
    onAuth(auth, session, callback) {
        let username = 'testuser';
        let password = 'testpass';

        // check username and password
        if (
            auth.username === username &&
            (auth.method === 'CRAM-MD5'
                ? auth.validatePassword(password) // if cram-md5, validate challenge response
                : auth.password === password) // for other methods match plaintext passwords
        ) {
            return callback(null, {
                user: 'userdata' // value could be an user id, or an user object etc. This value can be accessed from session.user afterwards
            });
        }

        return callback(new Error('Authentication failed'));
    },

    // Validate MAIL FROM envelope address. Example allows all addresses that do not start with 'deny'
    // If this method is not set, all addresses are allowed
    onMailFrom(address, session, callback) {
        if (/^deny/i.test(address.address)) {
            return callback(new Error('Not accepted'));
        }
        callback();
    },

    // Validate RCPT TO envelope address. Example allows all addresses that do not start with 'deny'
    // If this method is not set, all addresses are allowed
    onRcptTo(address, session, callback) {
        let err;

        if (/^deny/i.test(address.address)) {
            return callback(new Error('Not accepted'));
        }

        // Reject messages larger than 100 bytes to an over-quota user
        if (address.address.toLowerCase() === 'almost-full@example.com' && Number(session.envelope.mailFrom.args.SIZE) > 100) {
            err = new Error('Insufficient channel storage: ' + address.address);
            err.responseCode = 452;
            return callback(err);
        }

        callback();
    },

    // Handle message stream
    onData(stream, session, callback) {
        stream.pipe(process.stdout);
        stream.on('end', () => {
            let err;
            if (stream.sizeExceeded) {
                err = new Error('Error: message exceeds fixed maximum message size 10 MB');
                err.responseCode = 552;
                return callback(err);
            }
            callback(null, 'Message queued as abcdef'); // accept the message once the stream is ended
        });
    }
});

server.on('error', err => {
    console.log('Error occurred');
    console.log(err);
});

// start listening
server.listen(SERVER_PORT, SERVER_HOST);