server.json5

{
  // Hostname to declare in welcome message.
  hostname: "example.com",

  // Interface the server will bind too (default: ::).
  bind: "::",

  // Port the server will listen too (default: 25).
  port: 25,

  // Number of connections to be allowed in the backlog (default: 25).
  backlog: 25,

  // Maximum number of SMTP transactions to process ofver a connection.
  transactionsLimit: 200,

  // Number of SMTP errors to allow before terminating connection (default: 3).
  errorLimit: 3,

  // Advertise AUTH support (default: true).
  auth: true,

  // Advertise STARTTLS support (default: true).
  starttls: true,

  // Advertise CHUNKING support (default: true).
  chunking: true,

  // Java keystore (default: /usr/local/keystore.jks).
  keystore: "/usr/local/keystore",

  // Keystore password.
  keystorepassword: "avengers",

  // Email storage configuration.
  storage: {
    enabled: true,

    // Path to storage folder.
    path: "/usr/local/store",

    // Auto clean storage on service start.
    clean: true,

    // Auto clean delete matching filenames only.
    patterns: [
      "^([0-9]{8}\\.)"
    ]
  },

  // Users allowed to authorize to the server.
  users: [
    {
      name: "tony@example.com",
      pass: "giveHerTheRing"
    }
  ],

  // Predefined server response scenarios based on EHLO value.
  scenarios: {

    // Default scenario to use if no others match.
    "*": {
      rcpt: [
        // Custom response for addresses matching value regex.
        {
          value: "friday\\-[0-9]+@example\\.com",
          response: "252 I think I know this user"
        }
      ]
    },

    // How to reject mail at different commands.
    "reject.com": {
      // Custom response for EHLO.
      ehlo: "501 Not talking to you",

      // Custom response for MAIL.
      mail: "451 I'm not listening to you",

      // Custom response for given recipients.
      rcpt: [
        {
          value: "ultron@reject\\.com",
          response: "501 Heart not found"
        }
      ],

      // Custom response for DATA.
      data: "554 Your data is corrupted"
    },

    // How to configure TLS for failure using a deprecated version and weak cipher.
    "failtls.com" : {

      // Custom response for STARTTLS.
      // STARTTLS also supports a list of protocols and ciphers to use handshake.
      starttls: {
        response: "220 You will fail",
        protocols: ["TLSv1.0"],
        ciphers: ["TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA"]
      }
    }
  }
}