Quick and dirty smtp server, that accepts handlers to process messages



smtp-tester is a simple smtp server that accepts connections, receives mail, and then calls callbacks that are bound to a particular address.


Installation is fairly straightforward, just install the npm module:

npm install smtp-tester

Starting an SMTP server

First, require smtp-tester:

var ms = require('smtp-tester');

Next, initialize a server with a port on which it should listen.

var mailServer = ms.init(port);

Done. Your SMTP server is now listening on port 'port'.

Sending Mail

Send mail using any SMTP client you want. For node work, I personally use nodemailer

npm install nodemailer

Receiving Mail

To receive mail, bind a handler to the mailServer you created earlier.

var ms, mailServer, handler, port = 4000;
ms = require('smtp-tester');
mailServer = ms.init(port);
handler = function(addr,id,email) {
    // do something interesting


Done. Every mail sent to every one sent before binding) will call the handler exactly once.

You can have as many handlers as you want, they are all executed, even for the same address. However, execution order, while usually in the order in which they were added, is not guaranteed.

If you intend to capture a single message using promises, you can do:

  .then(function({ address, id, email }) {
    // Do something interesting

Most likely you'll want to use the waitoption as well, so if no message is received in the given time frame, captureOne()rejects the promise:

mailServer.captureOne('', { wait: 1000 })
  .then(function({ address, id, email }) {
    // Do something interesting
  .catch(function(error) {
    // No message delivered to in 1 second.

Now using async/await:

try {
  const { email } = await mailServer.captureOne('', { wait: 1000 });
} catch (error) {
  // No message delivered to in 1 second.

This is useful for testing that nomessage was delivered, too.

Catch-All Handlers

If you want a handler to catch every email that is sent through the system, just bind with no address at all.

handler = function(addr,id,email) {
    // do something interesting
    // because this is a catch-all, the addr will be null

Catch-All handlers are alwaysrun before specific handlers.

Stopping Receipt

To stop receiving mail at a particular handler, just unbind.

Catch-All Handlers

If you want to remove a catch-all handler that catches every email that is sent through the system, just unbind with no address at all.

handler = function(addr,id,email) {
    // do something interesting
    // because this is a catch-all, the addr will be null
mailServer.bind(handler); // this adds it
mailServer.unbind(handler); // this removes it

Removing Messages

To remove messages from the mail server, you can remove an individual message or all of them:


Stopping the Server

Surprisingly, the method is just called "stop".



Handlers that receive mail are passed three parameters.

  • addr: Address to which the email was addressed, and for which the handler was bound. If this is a catch-all handler, then this is null.
  • id: Internal ID of the email in this mail server process. Useful for removing messages or checking against something in our cache.
  • email: JavaScript object of the email, containing "sender", "receivers", "data" (raw text), "headers", "body" (plain text) and "html".

Sample email object is as follows, taken from the test.js included with the package.

  sender:    '',
  receivers: {
    '': true
  data:      'X-Mailer: Nodemailer (0.2.3; +\r\nDate: Thu, 01 Dec 2011 10:24:01 GMT\r\nFrom:\r\nTo:\r\nSubject: email test\r\nMIME-Version: 1.0\r\nContent-Type: text/plain; charset=UTF-8\r\nContent-Transfer-Encoding: quoted-printable\r\n\r\nThis is a test mail',
  body:      'This is a test mail',
  headers: {
    'x-mailer':                  'Nodemailer (0.2.3; +',
    date:                        'Thu, 01 Dec 2011 10:24:01 GMT',
    from:                        '',
    to:                          '',
    subject:                     'email test',
    'mime-version':              '1.0',
    'content-type':              { value: 'text/plain' },
    'content-transfer-encoding': 'quoted-printable'


smtp-tester supports pre-shipped modules. They are named and can be run by calling

var success;
// to load a module
success = mailServer.module(name);

// to unload a module

If the module successfully loads, it will return success, else it will return false.

The following modules are currently available.

  • logAll: logs every message received to the console in a text format close to raw text.

More are expected to follow.


Just run

npm test

Note that each build triggers a Travis CI build




  • 解析 SMTP 协议

    SMTP 是属于应用层协议, 是基于 TCP 协议用于收发邮件的.我们常常需要在业务中使用邮件, 但是并没有对 smtp 协议有足够的了解, 我们下面就来全面地了解一下. smtp 服务器一般会开启 ...

    2 年前
  • xmpp-smtp-gw

    xmpp smtp gateway XMPP SMTP Gateway build status(

    3 个月前
  • web-component-tester

    webcomponenttester makes testing your web components a breeze NPM version(

    1 年前
  • typings-tester

    TypeScript definition testing library Typings Tester npm versionnpmimagenpmurl Build Statustravisi...

    2 年前
  • typescript-definition-tester

    Purpose The purpose of this repository is to wrap the TypeScript compiler so that a consumer can...

    2 个月前
  • tree-layout-tester

    Tests cases for various tree layout algorithms treelayouttester ================== Checks a tree la...

    2 个月前
  • textlint-tester

    testing tool for textlint rule. textlinttester Mocha( "Mocha") test helper lib...

    10 个月前
  • tester

    Unit testing made simple and fun: flat colors and emoji in your tests. tester Support me on P...

    2 年前
  • stylelint-rule-tester

    An easy way to test stylelint rules stylelintruletester An easy way to test stylelint(https://git...

    8 个月前
  • smtp-tester-bin

    cli script for the library smtptesterbin This is a simple wrapper for running @deitch's (https:/...

    7 个月前


扫码加入 JavaScript 社区