A framework for writing conversational email responders
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Build Status Coverage Status License: MIT

Fuse - automating email conversations

A framework for writing conversational email responders

SparkPost is a cloud email service that allows developers to send and receive emails.

This is a botkit-inspired framework written around the SparkPost API to make it easy to automate email conversations.

Table of Contents

Getting Started
Start Listening
The Address Object
Receiving Messages
Sending Messages
Having Conversations
Helper Functions

Getting Started

Before setting this framework up you'll first need a SparkPost account. SparkPost lets you send 15,000 emails per month for free with their Developer Account which should be plenty to get started. You can sign up here.

Creating an API Key

For this framework to work, you will need to create an API Key with the following access:

Sending Domains: Read/Write
Inbound Domains: Read/Write
Relay Webhooks: Read/Write
Transmissions: Read/Write

To create the key visit the API Keys section in the SparkPost app under Account. Once there selected the required permissions and store the generated key somewhere safe as you won't be able to access it again.

Configuring your sending domain

The sending domain is the domain that you will send emails from (.e.g. hi.there@sendingdomain.com).

Add your domain in the Sending Domains section. You'll need to verify ownership of the domain through the methods provided in the UI.

Configuring your inbound domain

Your inbound domain is the domain at which you will receive emails. It can be the same address as your sending domain.

Add the following MX records to your inbound domain's DNS

Name Type Data Priority
your.inbounddomain.com MX rx1.sparkpostmail.com 10
your.inbounddomain.com MX rx2.sparkpostmail.com 10
your.inbounddomain.com MX rx3.sparkpostmail.com 10

Setting up your fuse

Once the DNS changes have propagated (you can check the mxtoolbox), its time to build your responder.


npm install fuse-email



  • config.email_key
    • Required: yes
    • Type: String
    • An API Key
  • config.sending_address
    • Required: yes
    • Type: String
    • A valid email for the responder to send mail from
  • config.inbound_address
    • Required: yes
    • Type: String
    • A valid email for the responder to receive mail at
  • config.domain
    • Required: yes
    • Type: String
    • The domain you are using to host your responder
  • config.endpoint
    • Required: no
    • Type: String
    • Default: /relay
    • The path to send the relay webhook to
  • config.name
    • Required: no
    • Type: String
    • Default: Sparky
    • The name of your responder
  • config.auth_token
    • Required: no
    • Type: String
    • An Authentication Token for the relay webhook to use to verify its identity
  • config.size_limit
    • Required: no
    • Type: String
    • Default: 50mb
    • The maximum post size - if you get request entity too large errors increase this.
  • config.restrict_inbound
    • Required: no
    • Type: Boolean
    • Default: true
    • Whether or not to process inbound emails that were sent to an different email address
  • config.transport
    • Required: no
    • Type: String
    • Default: sparkpost
    • The transport to use

Next you'll need to create a Fuse instance

var Fuse = require('fuse-email');

var fuse = Fuse({
  email_key: 'SPARKPOST_API_KEY',
  name: 'NAME',
  sending_address: 'robot@MY_SENDING_DOMAIN',
  inbound_address: 'robot@MY_INBOUND_DOMAIN',
  domain: 'MY_DOMAIN'

Start Listening


Runs the setup for the transport. This will make sure you are setup correctly with your transport. Do not use this in production.

fuse.setupTransport(function() {
  // setup the server and endpoint

fuse.setupServer(port, callback)

Starts an express server at the given port. The callback is called when the server is running.

fuse.setupServer(3000, function(err, server) {
  // the server is up

fuse.setupEndpoint(server, callback)

Sets up an endpoint based on config.endpoint to receive the data from the relay webhook from SparkPost.

fuse.setupServer(3000, function(err, server) {
  fuse.setupEndpoint(server, function() {
  	// fuse is now running

The Address Object

All email addresses are in the following format

  email: 'email@example.com',
  name: 'My Name'

Receiving Messages

The events

Name Description
direct_email The responder received an email as an original recipient
cc_email The responder received an email as a cc'd recipient
bcc_email The responder received an email as a bcc'd recipient
email_received The responder received an email - this always fires unless there is a conversation happening

The inboundMessage object

The inboundMessage object is returned to the event listeners.

Name Type Description
inboundMessage.id String The message id of the inboundMessage
inboundMessage.event String The event that triggered the callback
inboundMessage.to Object The address object that received this email. Unless restrict_inbound is set to false, the to.email will always be your inbound_address
inboundMessage.from Object The address object who sent this email
inboundMessage.subject String The email subject
inboundMessage.text String The plaintext email body
inboundMessage.html String The html email body
inboundMessage.recipients Array[Object] An array of the address objects of the original recipients
inboundMessage.cc Array[Object] An array of the address objects of the cc'd recipients
inboundMessage.bcc Array[Object] An array of the address objects of the bcc'd recipients
inboundMessage.headers Object An object of the headers from the inbound email in a {key: value} format where value is a string if there is one value and an Array if two or more.
inboundMessage.attachments Array An array of attachments from the email
inboundMessage._raw * The original data received. For a SparkPost example look at the relay_message value here.
Attachments example
attachments = [{
    contentType: 'image/png',
    fileName: 'image.png',
    contentDisposition: 'attachment',
    contentId: '5.1321281380971@localhost',
    transferEncoding: 'base64',
    length: 126,
    generatedFileName: 'image.png',
    checksum: 'e4cef4c6e26037bcf8166905207ea09b',
    content: <Buffer ...>

Registering Event Listeners

There are two methods for receiving messages: on and hear. Both of these functions take a callback. These callbacks are given a responder object and a inboundMessage object.

fuse.on(events, callback)

To stop all subsequent listeners, return false

Name Type Description
events String or Array A comma delaminated list or an array of events on which to run this function
callback Function The function to be called when any of the given events take place


fuse.on('email_received', function(responder, inboundMessage) {
    subject: 'Hello World',
    body: 'What a nice day we are having!'

fuse.hears(patterns, events, callback)

If a message matches a hears listener all subsequent listeners are ignored.

The hears function works just like the on function except it takes an extra parameter, patterns. This parameter can be either an array or object. If it's an array then the patterns are checked against the subject and body. If it's an object then it can have a subject and/or body property, each of which should be an array of patterns to check against. All the patterns should either be Regular Expressions or strings.


  subject: ['hello', 'hi'],
  body: ['howdy', 'sup'],
}, 'direct_email', function(responder, inboundMessage) {
    subject: 'Hello there',
    body: 'Hello to you too!'

Sending Messages

The responder object

The responder object drives responding to messages. It is returned to all event listeners. You can create a standalone responder to send something or start a conversation by calling the responder method.

var responder = fuse.responder();

Keep in mind that the reply and startPrivateConversation methods will not work as they are reactions to inbound messages.

The outboundMessage object

Name Type Description
message.subject String The subject of the email.
message.body or message.html String The body of the email.
message.text String If this is not given then it will be generated from the html.
message.headers Object Email headers other than “Subject”, “From”, “To”, and “Reply-To”
message.recipients Array[Object] An array of email addresses.
message.cc Array[Object] An array of email addresses to receive a carbon copy.
message.bcc Array[Object] An array of email addresses to receive a blind carbon copy.
message.substitution_data String Any substitution data for the email.
message.attachments Array An array of attachments to send with the email. See the SparkPost docs for more details.
message.from Object An address object to override config.name and config.sending_address for this message.
message.reply_to Object An address object to override config.name and config.inbound_address for this message.


This will send send a new email with the given content. If recipients of any type are given the recipients and cc will default to the values from the received email.

fuse.on('direct_email', function(responder, inboundMessage) {
    subject: 'Hello World',
    body: '<h2>What a nice {{time}} we are having!</h2>',
    substitution_data: {
    	time: 'day'


This method is identical to the send method except it will reply to the sent message. As such you can not set the subject, recipients, or cc.

fuse.on('email_received', function(responder, inboundMessage) {
    body: 'I got your message!'

Having Conversations

The responder has two methods for starting conversations.

responder.startConversation(config, callback)

Starts a conversation with everyone from the received message or the specified recipients and cc recipients.

Name Type Required Description
config String or Object yes If this is a string then it is the subject of the conversation.
config.subject String yes The subject for the new thread of messages for this conversation. This is required.
config.recipients Array[Object] no An array of address objects. This will default to the recipients of the inboundMessage that was returned with this responder. This is required if starting a conversation from a standalone responder.
config.cc Array[Object] no An array of address objects to receive a carbon copy. This will default to the cc'd recipients of the inboundMessage that was returned with this responder.
config.timeout_after Number no Milliseconds to wait before the conversation times out. Defaults to 600000. (10 minutes).

responder.startPrivateConversation(topic, callback)

Starts a conversation with the person who sent the inboundMessage. This can not be used from a standalone responder.

the convo object

When a conversation is started it the callback receives a convo object.


This works just like the reply method of the responder object. It will send the message to all the participants of this conversation.

convo.ask(outboundMessage, handler)

Name Type Description
message Object See the outboundMessage options
handler Function This will be called when someone replies to the question.

The handler function will receive a message object and the same convo object to continue the conversation.

// from event listener
responder.startConversation('Tell me about yourself!', function(convo) {
    body: 'What\'s your name?'
  }, function(convo, inboundMessage) {
    let name = sparky.clean(sparky.getLatest(inboundMessage));

      body: 'Nice to meet you, {{name}}',
      substitution_data: {
        name: name




This function keeps the conversation alive while preforming asynchronous tasks until you can ask a question. See an example here.


Call this function to force the conversation to end.

Util functions

These are a few functions to make your life easier.


Returns the given string stripped of any html tags, trailing spaces, and line breaks.


Returns the latest text message from an email thread.