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Easy as cake e-mail sending from your Node.js applications


Send e-mails from Node.js ‚Äď easy as cake! ūüćį‚úČÔłŹ

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Other similar packages you might be interested in

  • smtp-server ‚Äď add SMTP server interface to your application
  • smtp-connection ‚Äď connect to SMTP servers from your application
  • zone-mta ‚Äď full featured outbound MTA built using smtp-connection and smtp-server modules

Notes and information

Nodemailer supports

  • Node.js 0.10+, no ES6 shenanigans used that would break your production app
  • Unicode to use any characters, including full emoji support ūüĎĽ
  • Windows ‚Äď you can install it with npm on Windows just like any other module, there are no compiled dependencies. Use it from Azure or from your Windows box hassle free.
  • HTML content as well as plain text alternative
  • Attachments (including attachment streaming for sending larger files)
  • Embedded images in HTML
  • Secure e-mail delivery using SSL/STARTTLS
  • Different transport methods, either using built-in SMTP transports or from external plugins
  • Custom plugin support for manipulating messages (add DKIM signatures, use markdown content instead of HTML etc.)
  • Sane XOAUTH2 login with automatic access token generation (and feedback about the updated tokens)
  • Simple built-in templating using node-email-templates or custom renderer
  • Proxies for SMTP connections (SOCKS, HTTP and custom connections)

See Nodemailer homepage for complete documentation

Support Nodemailer development

Donate to author

If you want to support with Bitcoins, then my wallet address is 15Z8ADxhssKUiwP3jbbqJwA21744KMCfTM

TL;DR Usage Example

This is a complete example to send an e-mail with plaintext and HTML body

var nodemailer = require('nodemailer');
// create reusable transporter object using the default SMTP transport 
var transporter = nodemailer.createTransport('smtps://');
// setup e-mail data with unicode symbols 
var mailOptions = {
    to: ',', // list of receivers 
// send mail with defined transport object 
transporter.sendMail(mailOptions, function(error, info){
        return console.log(error);
    console.log('Message sent: ' + info.response);

To use Gmail you may need to configure "Allow Less Secure Apps" in your Gmail account unless you are using 2FA in which case you would have to create an Application Specific password. You also may need to unlock your account with "Allow access to your Google account" to use SMTP.

Setting up

Install with npm

npm install nodemailer

To send e-mails you need a transporter object

var transporter = nodemailer.createTransport(transport[, defaults])


  • transporter is going to be an object that is able to send mail
  • transport is the transport configuration object, connection url or a transport plugin instance
  • defaults is an object that defines default values for mail options

You have to create the transporter object only once. If you already have a transporter object you can use it to send mail as much as you like.

Send using SMTP

SMTP? Say what?

You might wonder why you would need to set something up while in comparison PHP's mail command works out of the box with no special configuration whatsoever. Just call mail(...) and you're already sending mail. So what's going on in Node.js?

The difference is in the software stack required for your application to work. While Node.js stack is thin, all you need for your app to work is the node binary, then PHP's stack is fat. The server you're running your PHP code on has several different components installed. Firstly the PHP interpreter itself. Then there's some kind of web server, most probably Apache or Nginx. Web server needs some way to interact with the PHP interpreter, so you have a CGI process manager. There might be MySQL also running in the same host. Depending on the installation type you might even have imagemagick executables or other helpers lying around somewhere. And finally, you have the sendmail binary.

What PHP's mail() call actually does is that it passes your mail data to sendmail's stdin and thats it, no magic involved. sendmail does all the heavy lifting of queueing your message and trying to send it to the recipients' MX mail server. Usually this works because the server is an actual web server accessible from the web and has also gathered some mail sending reputation because PHP web hosts have been around for, like, forever.

Node.js apps on the other hand might run wherever, usually on some really new VPS behind an IP address that has no sending reputation at all. Or the IP is dynamically allocated which is the fastest way to get rejected while trying to send mail. So while you might actually emulate the same behavior with Nodemailer by using either the sendmail transport or so called direct transport, then this does not guarantee yet any deliverability. Recipient's server might reject connection from your app because your server has dynamic IP address. Or it might reject or send your mail straight to spam mailbox because your IP address is not yet trusted.

So the reason why PHP's mail works and Node.js's does not is that your PHP hosting provider has put in a lot of work over several years to provide a solid mail sending infrastructure. It is not about PHP at all, it is about the infrastructure around it.

Set up SMTP

You can use 3 kinds of different approaches when using SMTP

  1. normal usage. No specific configuration needed. For every e-mail a new SMTP connection is created and message is sent immediately. Used when the amount of sent messages is low.
  2. pooled usage. Set pool option to true to use it. A fixed amount of pooled connections are used to send messages. Useful when you have a large number of messages that you want to send in batches.
  3. direct usage. Set direct option to true to use it. SMTP connection is opened directly to recipients MX server, skipping any local SMTP relays. useful when you do not have a SMTP relay to use. Riskier though since messages from untrusted servers usually end up in the Spam folder.
var transporter = nodemailer.createTransport(options[, defaults])


  • options defines connection data
    • options.pool if set to true uses pooled connections (defaults to false), otherwise creates a new connection for every e-mail.
    • if set to true, bypasses MTA relay and connects directly to recipients MX. Easier to set up but has higher chances of ending up in the Spam folder
    • options.service can be set to the name of a well-known service so you don't have to input the port, host, and secure options (see Using well-known services)
    • options.port is the port to connect to (defaults to 25 or 465)
    • is the hostname or IP address to connect to (defaults to 'localhost')
    • if truethe connection will only use TLS. If false (the default), TLS may still be upgraded to if available via the STARTTLS command.
    • options.ignoreTLS if this is true and secure is false, TLS will not be used (either to connect, or as a STARTTLS connection upgrade command).
    • options.requireTLS if this is true and secure is false, it forces Nodemailer to use STARTTLS even if the server does not advertise support for it.
    • options.tls defines additional node.js TLSSocket options to be passed to the socket constructor, eg. {rejectUnauthorized: true}.
    • options.auth defines authentication data (see authentication section below)
    • options.authMethod defines preferred authentication method, eg. 'PLAIN'
    • optional hostname of the client, used for identifying to the server
    • options.localAddress is the local interface to bind to for network connections
    • options.connectionTimeout how many milliseconds to wait for the connection to establish
    • options.greetingTimeout how many milliseconds to wait for the greeting after connection is established
    • options.socketTimeout how many milliseconds of inactivity to allow
    • options.logger optional bunyan compatible logger instance. If set to true then logs to console. If value is not set or is false then nothing is logged
    • options.debug if set to true, then logs SMTP traffic, otherwise logs only transaction events. This option requires options.logger to be set, otherwise there is nowhere to log the transaction data
    • options.maxConnections available only if pool is set to true. (defaults to 5) is the count of maximum simultaneous connections to make against the SMTP server
    • options.maxMessages available only if pool is set to true. (defaults to 100) limits the message count to be sent using a single connection. After maxMessages messages the connection is dropped and a new one is created for the following messages
    • options.rateLimit available only if pool is set to true. (defaults to false) limits the message count to be sent in a second. Once rateLimit is reached, sending is paused until the end of the second. This limit is shared between connections, so if one connection uses up the limit, then other connections are paused as well
    • options.disableFileAccess if true, then does not allow to use files as content. Use it when you want to use JSON data from untrusted source as the email. If an attachment or message node tries to fetch something from a file the sending returns an error
    • options.disableUrlAccess if true, then does not allow to use Urls as content


var smtpConfig = {
    host: '',
    port: 465,
    secure: true, // use SSL 
    auth: {
        user: '',
        pass: 'pass'
var poolConfig = {
    pool: true,
    host: '',
    port: 465,
    secure: true, // use SSL 
    auth: {
        user: '',
        pass: 'pass'
var directConfig = {
    name: 'hostname' // must be the same that can be reverse resolved by DNS for your IP 

Alternatively you could use connection url. Use smtp:, smtps: or direct: as the protocol.

var smtpConfig = 'smtps://';
var poolConfig = 'smtps://';
var directConfig = 'direct:?name=hostname';

Proxy support

Nodemailer supports out of the box HTTP and SOCKS proxies for SMTP connections with the proxy configuration option. You can also use a custom connection handler with the getSocket method.

Proxy configuration is provided as a connection url where used protocol defines proxy protocol (eg. 'socks://hostname:port' for a SOCKS5 proxy). You can also use authentication by passing proxy username and password into the configuration url (eg 'socks://username:password@hostname:port')


HTTP proxy must support CONNECT tunnels (also called "SSL support") to SMTP ports. To use a HTTP/S server, provide a proxy option to SMTP configuration with the HTTP proxy configuration URL.

var smtpConfig = {
    host: '',
    port: 465,
    //proxy config 
    // assumes a HTTP proxy running on port 3128 
    proxy: 'http://localhost:3128/'

Possible protocol values for the HTTP proxy:

  • 'http:' if the proxy is running in a plaintext server
  • 'https:' if the proxy is running in a secure server

NB! Proxy protocol (http/s) does not affect how SMTP connection is secured or not

See an example of using a HTTP proxy here.


To use a HTTP/S server, provide a proxy option to SMTP configuration with the SOCKS4/5 proxy configuration URL.

var smtpConfig = {
    host: '',
    port: 465,
    //proxy config 
    // assumes a SOCKS5 proxy running on port 1080 
    proxy: 'socks5://localhost:1080/'

NB! When using SOCKS4, only an ipv4 address can be used

Possible protocol values for the SOCKS proxy:

  • 'socks4:' or 'socks4a:' for a SOCKS4 proxy
  • 'socks5:' or 'socks:' for a SOCKS5 proxy

See an example of using a SOCKS proxy here.

Custom connection handler

If you do not want to use SOCKS or HTTP proxies then you can alternatively provide a custom proxy handling code with the getSocket method. In this case you should initiate a new socket yourself and pass it to Nodemailer for usage.

// This method is called every time Nodemailer needs a new 
// connection against the SMTP server 
transporter.getSocket = function(options, callback){
    getProxySocketSomehow(options.port,, function(err, socket){
            return callback(err);
        callback(null, {
            connection: socket

Normally proxies provide plaintext sockets, so if the connection is supposed to use TLS then Nodemailer upgrades the socket from plaintext to TLS itself. If the socket is already upgraded then you can pass additional option secured: true to prevent Nodemailer from upgrading the already upgraded socket.

callback(null, {
    connection: socket,
    secured: true

See complete example using a custom socket connector here.



Applies to pooled SMTP connections. Emitted by the transport object if connection pool has free connection slots. Check if a connection is still available with isIdle() method (returns true if a connection is still available). This allows to create push-like senders where messages are not queued into memory in a Node.js process but pushed and loaded through an external queue like RabbitMQ.

var messages = [...'list of messages'];
transporter.on('idle', function(){
    // send next messages from the pending queue 
    while(transporter.isIdle() && messages.length){


If authentication data is not present, the connection is considered authenticated from the start. Set authentication data with options.auth

  • auth is the authentication object
    • auth.user is the username
    • auth.pass is the password for the user
    • auth.xoauth2 is the OAuth2 access token (preferred if both pass and xoauth2 values are set) or an XOAuth2 token generator object.

Using OAuth2

If a XOAuth2 token generator is used as the value for auth.xoauth2 then you do not need to set the value for user or pass. XOAuth2 generator generates required accessToken itself if it is missing or expired. In this case if the authentication fails, a new token is requested and the authentication is retried once. If it still fails, an error is returned.

NB! The correct OAuth2 scope for Gmail is

Install xoauth2 module to use XOauth2 token generators (not included by default)

npm install xoauth2 --save


var nodemailer = require('nodemailer');
var xoauth2 = require('xoauth2');
// listen for token updates (if refreshToken is set) 
// you probably want to store these to a db 
generator.on('token', function(token){
    console.log('New token for %s: %s', token.user, token.accessToken);
// login 
var transporter = nodemailer.createTransport({
    service: 'gmail',
    auth: {
        xoauth2: xoauth2.createXOAuth2Generator({
            user: '{username}',
            clientId: '{Client ID}',
            clientSecret: '{Client Secret}',
            refreshToken: '{refresh-token}',
            accessToken: '{cached access token}'

Using well-known services

If you do not want to specify the hostname, port and security settings for a well known service, you can use it by its name (case insensitive)

    service: 'gmail',
    auth: ..

See the list of all supported services here.

Verify SMTP connection configuration

You can verify your SMTP configuration with verify(callback) call (also works as a Promise). If it returns an error, then something is not correct, otherwise the server is ready to accept messages.

// verify connection configuration 
transporter.verify(function(error, success) {
   if (error) {
   } else {
        console.log('Server is ready to take our messages');

Send using a transport plugin

In addition to SMTP you can use other kind of transports as well with Nodemailer. See Available Transports below for known transports.

The following example uses nodemailer-ses-transport (Amazon SES).

var nodemailer = require('nodemailer');
var ses = require('nodemailer-ses-transport');
var transporter = nodemailer.createTransport(ses({
    accessKeyId: 'AWSACCESSKEY',
    secretAccessKey: 'AWS/Secret/key'

If the transport plugin follows common conventions, then you can also load it dynamically with the transport option. This way you would not have to load the transport plugin in your code (you do need to install the transport plugin though before you can use it), you only need to modify the configuration data accordingly.

var nodemailer = require('nodemailer');
var transporter = nodemailer.createTransport({
    transport: 'ses', // loads nodemailer-ses-transport 
    accessKeyId: 'AWSACCESSKEY',
    secretAccessKey: 'AWS/Secret/key'

Available Transports

Sending mail

Once you have a transporter object you can send mail with it:

transporter.sendMail(data[, callback])


  • data defines the mail content (see e-mail message fields below)
  • callback is an optional callback function to run once the message is delivered or it failed
    • err is the error object if message failed
    • info includes the result, the exact format depends on the transport mechanism used
      • info.messageId most transports should return the final Message-Id value used with this property
      • info.envelope includes the envelope object for the message
      • info.accepted is an array returned by SMTP transports (includes recipient addresses that were accepted by the server)
      • info.rejected is an array returned by SMTP transports (includes recipient addresses that were rejected by the server)
      • info.pending is an array returned by Direct SMTP transport. Includes recipient addresses that were temporarily rejected together with the server response
      • info.response is a string returned by SMTP transports and includes the last SMTP response from the server

If the message includes several recipients then the message is considered sent if at least one recipient is accepted

If callback argument is not set then the method returns a Promise object. Nodemailer itself does not use Promises internally but it wraps the return into a Promise for convenience.

E-mail message fields

The following are the possible fields of an e-mail message:

Commmon fields:

  • from - The e-mail address of the sender. All e-mail addresses can be plain '' or formatted '"Sender Name" <>', see Address Formatting for details
  • to - Comma separated list or an array of recipients e-mail addresses that will appear on the To: field
  • cc - Comma separated list or an array of recipients e-mail addresses that will appear on the Cc: field
  • bcc - Comma separated list or an array of recipients e-mail addresses that will appear on the Bcc: field
  • subject - The subject of the e-mail
  • text - The plaintext version of the message as an Unicode string, Buffer, Stream or an attachment-like object ({path: '/var/data/...'})
  • html - The HTML version of the message as an Unicode string, Buffer, Stream or an attachment-like object ({path: 'http://...'})
  • attachments - An array of attachment objects (see below for details)

Advanced fields:

  • sender - An e-mail address that will appear on the Sender: field (always prefer from if you're not sure which one to use)
  • replyTo - An e-mail address that will appear on the Reply-To: field
  • inReplyTo - The message-id this message is replying to
  • references - Message-id list (an array or space separated string)
  • watchHtml - Apple Watch specific HTML version of the message. Same usage as with text or html
  • icalEvent ‚Äď iCalendar event to use as an alternative. Same usage as with text or html. Additionally you could set method property (defaults to 'PUBLISH'). See an example here
  • priority - Sets message importance headers, either 'high', 'normal' (default) or 'low'.
  • headers - An object or array of additional header fields (e.g. {"X-Key-Name": "key value"} or [{key: "X-Key-Name", value: "val1"}, {key: "X-Key-Name", value: "val2"}])
  • alternatives - An array of alternative text contents (in addition to text and html parts) (see below for details)
  • envelope - optional SMTP envelope, if auto generated envelope is not suitable (see below for details)
  • messageId - optional Message-Id value, random value will be generated if not set
  • date - optional Date value, current UTC string will be used if not set
  • encoding - identifies encoding for text/html strings (defaults to 'utf-8', other values are 'hex' and 'base64')
  • raw - existing MIME message to use instead of generating a new one. If this value is set then you should also set the envelope object (if required) as the provided raw message is not parsed. The value could be a string, a buffer, a stream or an attachment-like object.
  • textEncoding - force content-transfer-encoding for text values (either quoted-printable or base64). By default the best option is detected (for lots of ascii use quoted-printable, otherwise base64)
  • list - helper for setting List-* headers

All text fields (e-mail addresses, plaintext body, html body, attachment filenames) use UTF-8 as the encoding. Attachments are streamed as binary.

NB! When using readable streams as any kind of content and sending fails then Nodemailer does not abort the already opened but not yet finished stream automatically, you need to do this yourself

var htmlstream = fs.createReadStream('content.html');
transport.sendMail({html: htmlstream}, function(err){
        // check if htmlstream is still open and close it to clean up 


Attachment object consists of the following properties:

  • filename - filename to be reported as the name of the attached file, use of unicode is allowed. If you do not want to use a filename, set this value as false, otherwise a filename is generated automatically
  • content - String, Buffer or a Stream contents for the attachment
  • path - path to a file or an URL (data uris are allowed as well) if you want to stream the file instead of including it (better for larger attachments)
  • contentType - optional content type for the attachment, if not set will be derived from the filename property
  • contentDisposition - optional content disposition type for the attachment, defaults to 'attachment'
  • cid - optional content id for using inline images in HTML message source
  • encoding - If set and content is string, then encodes the content to a Buffer using the specified encoding. Example values: base64, hex, binary etc. Useful if you want to use binary attachments in a JSON formatted e-mail object.
  • headers - custom headers for the attachment node. Same usage as with message headers
  • raw - is an optional special value that overrides entire contents of current mime node including mime headers. Useful if you want to prepare node contents yourself

Attachments can be added as many as you want.


var mailOptions = {
    attachments: [
        {   // utf-8 string as an attachment 
            filename: 'text1.txt',
            content: 'hello world!'
        {   // binary buffer as an attachment 
            filename: 'text2.txt',
            content: new Buffer('hello world!','utf-8')
        {   // file on disk as an attachment 
            filename: 'text3.txt',
            path: '/path/to/file.txt' // stream this file 
        {   // filename and content type is derived from path 
            path: '/path/to/file.txt'
        {   // stream as an attachment 
            filename: 'text4.txt',
            content: fs.createReadStream('file.txt')
        {   // define custom content type for the attachment 
            filename: 'text.bin',
            content: 'hello world!',
            contentType: 'text/plain'
        {   // use URL as an attachment 
            filename: 'license.txt',
            path: ''
        {   // encoded string as an attachment 
            filename: 'text1.txt',
            content: 'aGVsbG8gd29ybGQh',
            encoding: 'base64'
        {   // data uri as an attachment 
            path: 'data:text/plain;base64,aGVsbG8gd29ybGQ='


In addition to text and HTML, any kind of data can be inserted as an alternative content of the main body - for example a word processing document with the same text as in the HTML field. It is the job of the e-mail client to select and show the best fitting alternative to the reader. Usually this field is used for calendar events and such.

Alternative objects use the same options as attachment objects. The difference between an attachment and an alternative is the fact that attachments are placed into multipart/mixed or multipart/related parts of the message white alternatives are placed into multipart/alternative part.

Usage example:

var mailOptions = {
    html: '<b>Hello world!</b>',
    alternatives: [
            contentType: 'text/x-web-markdown',
            content: '**Hello world!**'

Alternatives can be added as many as you want.


Most messages do not need any kind of tampering with the headers. If you do need to add custom headers either to the message or to an attachment/alternative, you can add these values with the headers option. Values are processed automatically, non-ascii strings are encoded as mime-words and long lines are folded.

var mail = {
    headers: {
        'x-my-key': 'header value',
        'x-another-key': 'another value'
// X-My-Key: header value 
// X-Another-Key: another value 

Multiple rows

The same header key can be used multiple times if the header value is an Array

var mail = {
    headers: {
        'x-my-key': [
            'value for row 1',
            'value for row 2',
            'value for row 3'
// X-My-Key: value for row 1 
// X-My-Key: value for row 2 
// X-My-Key: value for row 3 

Prepared headers

Normally all headers are encoded and folded to meet the requirement of having plain-ASCII messages with lines no longer than 78 bytes. Sometimes it is preferable to not modify header values and pass these as provided. This can be achieved with the prepared option:

var mail = {
    headers: {
        'x-unprocessed': {
            prepared: true,
// X-Processed: a really long header or value with non-ascii characters 
//  =?UTF-8?Q?=F0=9F=91=AE?= 

Address Formatting

All the e-mail addresses can be plain e-mail addresses

or with formatted name (includes unicode support)


Notice that all address fields (even from:) are comma separated lists, so if you want to use a comma in the name part, make sure you enclose the name in double quotes: "–ú–į–Ļ–Ľ–Ķ—Ä, –Ě–ĺ–ī–Ķ" <>

or as an address object (in this case you do not need to worry about the formatting, no need to use quotes etc.)

    address: ''

All address fields accept comma separated list of e-mails or an array of e-mails or an array of comma separated list of e-mails or address objects - use it as you like. Formatting can be mixed.


You can even use unicode domains, these are automatically converted to punycode


SMTP envelope

SMTP envelope is usually auto generated from from, to, cc and bcc fields but if for some reason you want to specify it yourself (custom envelopes are usually used for VERP addresses), you can do it with envelope property.

envelope is an object with the following params: from, to, cc and bcc just like with regular mail options. You can also use the regular address format, unicode domains etc.

mailOptions = {
    from: '', // listed in rfc822 message header 
    to: '', // listed in rfc822 message header 
    envelope: {
        from: '"Daemon" <>', // used as MAIL FROM: address for SMTP 
        to: ', "Mailer" <>' // used as RCPT TO: address for SMTP 

Not all transports can use the envelope object, for example SES ignores it and only uses the data from the From:, To: etc. headers.

Using Embedded Images

A new alternative to cid embedded images is available! See nodemailer-base64-to-s3 for more information.

Attachments can be used as embedded images in the HTML body. To use this feature, you need to set additional property of the attachment - cid (unique identifier of the file) which is a reference to the attachment file. The same cid value must be used as the image URL in HTML (using cid: as the URL protocol, see example below).

NB! the cid value should be as unique as possible!

var mailOptions = {
    html: 'Embedded image: <img src=""/>',
    attachments: [{
        filename: 'image.png',
        path: '/path/to/file',
        cid: '' //same cid value as in the html img src 

Using templates

Nodemailer allows to use simple built-in templating or alternatively external renderers for common message types.

var transporter = nodemailer.createTransport(...);
var send = transporter.templateSender(templates, [defaults]);
// send a message based on provided templates 
send(mailData, context, callback);
// or 
send(mailData, context).then(...).catch(...);


  • templates is an object with template strings for built-in renderer or an EmailTemplate object for more complex rendering
// built-in renderer 
var send = transporter.templateSender({
    subject: 'This template is used for the "subject" field',
    text: 'This template is used for the "text" field',
    html: 'This template is used for the "html" field'
// external renderer 
var EmailTemplate = require('email-templates').EmailTemplate;
var send = transporter.templateSender(new EmailTemplate('template/directory'));
  • defaults is an optional object of message data fields that are set for every message sent using this sender
  • mailData includes message fields for current message
  • context is an object with template replacements, where key replaces {{key}} when using the built-in renderer
var templates = {
    text: 'Hello {{username}}!'
var context = {
    username: 'User Name'
// results in "Hello, User Name!" as the text body 
// of the message when using built-in renderer 
  • callback is the transporter.sendMail callback (if not set then the function returns a Promise)

NB! If using built-in renderer then template variables are HTML escaped for the html field but kept as is for other fields

Example 1. Built-in renderer

var transporter = nodemailer.createTransport('smtps://');
// create template based sender function 
var sendPwdReset = transporter.templateSender({
    subject: 'Password reset for {{username}}!',
    text: 'Hello, {{username}}, Please go here to reset your password: {{ reset }}',
    html: '<b>Hello, <strong>{{username}}</strong>, Please <a href="{{ reset }}">go here to reset your password</a>: {{ reset }}</p>'
}, {
    from: '',
// use template based sender to send a message 
    to: ''
}, {
    username: 'Node Mailer',
    reset: '<unique-single-use-token>'
}, function(err, info){
        console.log('Password reset sent');

Example 2. External renderer

var EmailTemplate = require('email-templates').EmailTemplate;
var transporter = nodemailer.createTransport('smtps://');
// create template based sender function 
// assumes text.{ext} and html.{ext} in template/directory 
var sendPwdReminder = transporter.templateSender(new EmailTemplate('template/directory'), {
    from: '',
// use template based sender to send a message 
    to: '',
    // EmailTemplate renders html and text but no subject so we need to 
    // set it manually either here or in the defaults section of templateSender() 
    subject: 'Password reminder'
}, {
    username: 'Node Mailer',
    password: '!"\'<>&some-thing'
}, function(err, info){
        console.log('Password reminder sent');

Custom renderer

In addition to the built-in and node-email-templates based renderers you can also bring your own.

var sendPwdReminder = transporter.templateSender({
    render: function(context, callback){
        callback(null, {
            html: 'rendered html content',
            text: 'rendered text content'

Example. Using swig-email-templates

var EmailTemplates = require('swig-email-templates');
var transporter = nodemailer.createTransport('smtps://');
// create template renderer 
var templates = new EmailTemplates();
// provide custom rendering function 
var sendPwdReminder = transporter.templateSender({
    render: function(context, callback){
        templates.render('pwreminder.html', context, function (err, html, text) {
                return callback(err);
            callback(null, {
                html: html,
                text: text

List-* headers

Nodemailer includes a helper for setting more complex List-* headers with ease. Use message option list to provide all list headers. You do not need to add protocol prefix for the urls, or enclose the url between < and >, this is handled automatically.

If the value is a string, it is treated as an URL. If you want to provide an optional comment, use {url:'url', comment: 'comment'} object. If you want to have multiple header rows for the same List-* key, use an array as the value for this key. If you want to have multiple URLs for single List-* header row, use an array inside an array.

List-* headers are treated as pregenerated values, this means that lines are not folded and strings are not encoded. Use only ascii characters and be prepared for longer header lines.

var mailOptions = {
    list: {
        // List-Help: <> 
        help: '',
        // List-Unsubscribe: <> (Comment) 
        unsubscribe: {
            url: '',
            comment: 'Comment'
        // List-Subscribe: <> 
        // List-Subscribe: <> (Subscribe) 
        subscribe: [
                url: '',
                comment: 'Subscribe'
        // List-Post: <>, <> (Post) 
        post: [
                    url: '',
                    comment: 'Post'

Available Plugins

In addition to built-in e-mail fields you can extend these by using plugins.

Using Gmail

Even though Gmail is the fastest way to get started with sending emails, it is by no means a preferable solution unless you are using OAuth2 authentication. Gmail expects the user to be an actual user not a robot so it runs a lot of heuristics for every login attempt and blocks anything that looks suspicious to defend the user from account hijacking attempts. For example you might run into trouble if your server is in another geographical location ‚Äď everything works in your dev machine but messages are blocked in production.

Additionally Gmail has came up with the concept of 'less secure' apps which is basically anyone who uses plain password to login to Gmail, so you might end up in a situation where one username can send (support for 'less secure' apps is enabled) but other is blocked (support for 'less secure' apps is disabled). When using this method make sure to enable the required functionality by completing the "captcha enable". Without this, less secure connections won't work.

To prevent having login issues you should either use XOAUTH2 (see details here) or use another provider and preferably a dedicated one like Mailgun or SendGrid or any other. Usually these providers have free plans available that are comparable to the daily sending limits of Gmail. Gmail has a limit of 500 recipients a day (a message with one To and one Cc address counts as two messages since it has two recipients) for addresses and 2000 for Google Apps customers, larger SMTP providers usually offer about 200-300 recipients a day for free.

Delivering Bulk Mail

Here are some tips how to handle bulk mail, for example if you need to send 10 million messages at once (originally published as a blog post).

  1. Use a dedicated SMTP provider like SendGrid or Mailgun or any other. Do not use services that offer SMTP as a sideline or for free (that's Gmail or the SMTP of your homepage hosting company) to send bulk mail ‚Äď you'll hit all the hard limits immediatelly or get labelled as spam. Basically you get what you pay for and if you pay zero then your deliverability is near zero as well. E-mail might seem free but it is only free to a certain amount and that amount certainly does not include 10 million e-mails in a short period of time.
  2. Use a dedicated queue manager, for example RabbitMQ for queueing the e-mails. Nodemailer creates a callback function with related scopes etc. for every message so it might be hard on memory if you pile up the data for 10 million messages at once. Better to take the data from a queue when there's a free spot in the connection pool (previously sent message returns its callback). See rabbit-queue for an example of using RabbitMQ queues with Nodemailer connection pool.
  3. Use nodemailer-smtp-pool transport. You do not want to have the overhead of creating a new connection and doing the SMTP handshake dance for every single e-mail. Pooled connections make it possible to bring this overhead to a minimum.
  4. Set maxMessages option to Infinity for the nodemailer-smtp-pool transport. Dedicated SMTP providers happily accept all your e-mails as long you are paying for these, so no need to disconnect in the middle if everything is going smoothly. The default value is 100 which means that once a connection is used to send 100 messages it is removed from the pool and a new connection is created.
  5. Set maxConnections to whatever your system can handle. There might be limits to this on the receiving side, so do not set it to Infinity, even 20 is probably much better than the default 5. A larger number means a larger amount of messages are sent in parallel.
  6. Use file paths not URLs for attachments. If you are reading the same file from the disk several million times, the contents for the file probably get cached somewhere between your app and the physical hard disk, so you get your files back quicker (assuming you send the same attachment to all recipients). There is nothing like this for URLs ‚Äď every new message makes a fresh HTTP fetch to receive the file from the server.
  7. If the SMTP service accepts HTTP API as well you still might prefer SMTP and not the HTTP API as HTTP introduces additional overhead. You probably want to use HTTP over SMTP if the HTTP API is bulk aware ‚Äď you send a message template and the list of 10 million recipients and the service compiles this information into e-mails itself, you can't beat this with SMTP.

Implementing plugins and transports

There are 3 stages a plugin can hook to

  1. 'compile' is the step where e-mail data is set but nothing has been done with it yet. At this step you can modify mail options, for example modify html content, add new headers etc. Example: nodemailer-markdown that allows you to use markdown source instead of text and html.
  2. 'stream' is the step where message tree has been compiled and is ready to be streamed. At this step you can modify the generated MIME tree or add a transform stream that the generated raw e-mail will be piped through before passed to the transport object. Example: nodemailer-dkim that adds DKIM signature to the generated message.
  3. Transport step where the raw e-mail is streamed to destination. Example: nodemailer-smtp-transport that streams the message to a SMTP server.

Including plugins

'compile' and 'stream' plugins can be attached with use(plugin) method

transporter.use(step, pluginFunc)


  • transporter is a transport object created with createTransport
  • step is a string, either 'compile' or 'stream' that defines when the plugin should be hooked
  • pluginFunc is a function that takes two arguments: the mail object and a callback function

Plugin API

All plugins (including transports) get two arguments, the mail object and a callback function.

Mail object that is passed to the plugin function as the first argument is an object with the following properties:

  • data is the mail data object that is passed to the sendMail method
  • message is the BuildMail object of the message. This is available for the 'stream' step and for the transport but not for 'compile'.
  • resolveContent is a helper function for converting Nodemailer compatible stream objects into Strings or Buffers


If your plugin needs to get the full value of a param, for example the String value for the html content, you can use resolveContent() to convert Nodemailer compatible content objects to Strings or Buffers.

data.resolveContent(obj, key, callback)


  • obj is an object that has a property you want to convert to a String or a Buffer
  • key is the name of the property you want to convert
  • callback is the callback function with (err, value) where value is either a String or Buffer, depending on the input


function plugin(mail, callback){
    // if is a file or an url, it is returned as a Buffer 
    mail.resolveContent(, 'html', function(err, html){
            return callback(err);
        console.log('HTML contents: %s', html.toString());


Compile step plugins get only the object but not mail.message in the mail argument of the plugin function. If you need to access the mail.message as well use 'stream' step instead.

This is really straightforward, your plugin can modify the object at will and once everything is finished run the callback function. If the callback gets an error object as an argument, then the process is terminated and the error is returned to the sendMail callback.


The following plugin checks if text value is set and if not converts html value to text by removing all html tags.

transporter.use('compile', function(mail, callback){
    if(!mail.text && mail.html){
        mail.text = mail.html.replace(/<[^>]*>/g, ' ');

See plugin-compile.js for a working example.


Streaming step is invoked once the message structure is built and ready to be streamed to the transport. Plugin function still gets but it is included just for the reference, modifying it should not change anything (unless the transport requires something from the, for example

You can modify the mail.message object as you like, the message is not yet streaming anything (message starts streaming when the transport calls mail.message.createReadStream()).

In most cases you might be interested in the message.transform() method for applying transform streams to the raw message.


The following plugin replaces all tabs with spaces in the raw message.

var transformer = new (require('stream').Transform)();
transformer._transform = function(chunk, encoding, done) {
    // replace all tabs with spaces in the stream chunk 
    for(var i = 0; i < chunk.length; i++){
        if(chunk[i] === 0x09){
            chunk[i] = 0x20;
transporter.use('stream', function(mail, callback){
    // apply output transformer to the raw message stream 

See plugin-stream.js for a working example.

Additionally you might be interested in the message.getAddresses() method that returns the contents for all address fields as structured objects.


The following plugin prints address information to console.

transporter.use('stream', function(mail, callback){
    var addresses = mail.message.getAddresses();
    console.log('From: %s', JSON.stringify(addresses.from));
    console.log('To: %s', JSON.stringify(;
    console.log('Cc: %s', JSON.stringify(;
    console.log('Bcc: %s', JSON.stringify(addresses.bcc));


Transports are objects that have a method send and properties name and version. Additionally, if the transport object is an Event Emitter, 'log' events are piped through Nodemailer. A transport object is passed to the nodemailer.createTransport(transport) method to create the transporter object.

This is the name of the transport object. For example 'SMTP' or 'SES' etc. = require('package.json').name;


This should be the transport module version. For example '0.1.0'.

transport.version = require('package.json').version;

transport.send(mail, callback)

This is the method that actually sends out e-mails. The method is basically the same as 'stream' plugin functions. It gets two arguments: mail and a callback. To start streaming the message, create the stream with mail.message.createReadStream()

Callback function should return an info object as the second arugment. This info object should contain messageId value with the Message-Id header (without the surrounding < > brackets)

The following example pipes the raw stream to the console.

transport.send = function(mail, callback){
    var input = mail.message.createReadStream();
    var messageId = (mail.message.getHeader('message-id') || '').replace(/[<>\s]/g, '');
    input.on('end', function() {
        callback(null, {
            messageId: messageId


If your transport needs to be closed explicitly, you can implement a close method.

This is purely optional feature and only makes sense in special contexts (eg. closing a SMTP pool).


If your transport is able to notify about idling state by issuing 'idle' events then this method should return if the transport is still idling or not.

Wrapping up

Once you have a transport object, you can create a mail transporter out of it.

var nodemailer = require('nodemailer');
var transport = require('some-transport-method');
var transporter = nodemailer.createTransport(transport);
transporter.sendMail({mail data});

See minimal-transport.js for a working example.


Nodemailer is licensed under MIT license. Basically you can do whatever you want to with it

The Nodemailer logo was designed by Sven Kristjansen.