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Create emails addresses in Ruby then send and receive real emails and attachments. See https://www.mailslurp.com/ruby/ for full Ruby documentation. Get an API Key at https://app.mailslurp.com
 Project Readme

MailSlurp Ruby Client

Create real email addresses on demand. Send and receive emails and attachments from code and tests using Ruby.

MailSlurp is an email API service that lets you create real email addresses in code. You can then send and receive emails and attachments in Ruby applications and tests.

ruby smtp tutorial

Quick links

Common controllers

Example tutorials

Get started

This section describes how to get up and running with the Ruby client.

See the examples page for more examples and use with common frameworks such as Rails and RSpec.

See the method documentation for a list of all functions

Create API Key

First you'll need an API Key. Create a free account and copy the key from your dashboard.

Ruby requirements

The MailSlurp client requires Ruby 2.x or 3.x and the ruby-dev package. You most likely have these packages but if not:

sudo apt-get install ruby-dev

Install Gem

gem install mailslurp_client

Or in your Gemfile:

source "https://rubygems.org"

gem 'mailslurp_client'
gem 'typhoeus'

And then run bundler install:

gem install bundler
bundle install

Libcurl requirements

You may need to install typhoeus if you encounter libcurl errors.

gem 'typhoeus'

Configure the client

require 'mailslurp_client'

MailSlurpClient.configure do |config|
  config.api_key['x-api-key'] = ENV['API_KEY']

Create controllers

To call the API create a controller like this:

inbox_controller = MailSlurpClient::InboxControllerApi.new

Common uses

MailSlurp can be used for anything email related: sending and receiving emails, creating email addresses, or testing email processes.

Here are some common uses:

Create inboxes

To use MailSlurp you need to create inboxes. These are email accounts that have an ID and a real email address. See methods on the inbox controller for more information.

options = {
  name: "My test inbox",
  inboxType: "SMTP_INBOX"
inbox = inbox_controller.create_inbox_with_options(options)
assert_match /@mailslurp/, inbox.email_address

In a test:

it 'can create email addresses' do
    inbox_controller = MailSlurpClient::InboxControllerApi.new
    inbox = inbox_controller.create_inbox

    expect(inbox.id).not_to be_nil
    expect(inbox.email_address).to include("mailslurp.com")

More options

The create_inbox method has some limitations in the Ruby client. To create inboxes with more options use the alternative create_inbox_with_options method. (This uses a request body instead of query parameters.)

it 'can an inbox with tags' do
    inbox_controller = MailSlurpClient::InboxControllerApi.new
    # create an inbox with tags
    inbox = inbox_controller.create_inbox_with_options({
      tags: ['t1','t2'],
      description: "test with tags",
      name: "test name"

    # has tags
    expect(inbox.id).to be_truthy
    expect(inbox.description).to be_truthy
    expect(inbox.name).to be_truthy
    expect(inbox.tags).to include('t1')
    expect(inbox.tags).to include('t2')

    # can update tags
    inbox_updated = inbox_controller.update_inbox(inbox.id, {
      tags: ['newtag']
    expect(inbox_updated.tags).to eq(['newtag'])

Inbox types

Inboxes can be either SMTP or HTTP type. Set the inbox type using the inboxType property. SMTP inboxes are handled by a custom mailserver and support a wide range of clients while HTTP inboxes use Amazon SES and don't support some older clients like Outlook. SMTP inboxes are recommended for public facing email addresses while HTTP inboxes are best for application testing. Please see the guide on types of inboxes for more information.

Configure NET/SMTP access

SMTP type inboxes allow SMTP and IMAP access using unique host, port, password, and username. Use the inbox_controller.get_imap_smtp_access method to access SMTP credentials. Then configure net/smtp in Ruby to send email using SMTP.

it 'can send email using SMTP' do
  inbox_controller = MailSlurpClient::InboxControllerApi.new

  # create two inboxes
  inbox1 = inbox_controller.create_inbox_with_options({ inboxType: 'SMTP_INBOX' })
  inbox2 = inbox_controller.create_inbox

  expect(inbox1.email_address).to include('@mailslurp.mx')

  # get smtp access for inbox
  smtp_access = inbox_controller.get_imap_smtp_access({ inbox_id: inbox1.id })

  # compose email
  message = <<~MESSAGE_END
    From: #{inbox1.email_address}
    To: #{inbox2.email_address}
    Subject: Test smtp email

    This is a test

  # configure SMTP with host port and "PLAIN" authentication
  Net::SMTP.start(smtp_access.smtp_server_host, smtp_access.smtp_server_port, 'greeting.your.domain',
                  smtp_access.smtp_username, smtp_access.smtp_password, :plain) do |smtp|
    # send email
    smtp.send_message message, inbox1.email_address, inbox2.email_address

  # now confirm email was sent
  wait_for_controller = MailSlurpClient::WaitForControllerApi.new
  email = wait_for_controller.wait_for_latest_email({ inbox_id: inbox2.id })
  expect(email.subject).to include("Test smtp email")

List inboxes

Inboxes you create can be listed in a paginated way using the InboxController).

it 'can list inboxes' do
    inbox_controller = MailSlurpClient::InboxControllerApi.new
    paged_inboxes = inbox_controller.get_all_inboxes({ page: 0, size: 20 })

    # assert on pagination fields
    expect(paged_inboxes.content).not_to be_empty
    expect(paged_inboxes.number).to be(0)
    expect(paged_inboxes.size).to be(20)

    # can access inbox result
    expect(paged_inboxes.content[0].id).not_to be_empty

Send emails

You can send HTML emails easily with the inbox controller. First create an inbox then use its ID with the send_email method.

inbox_controller.send_email(inbox.id, {
  to: [inbox.email_address],
  subject: "Hello",
  body: "Welcome. Your code is: 123456",

To send attachments see the Method Documentation.

# create an inbox
inbox_controller = MailSlurpClient::InboxControllerApi.new
inbox = inbox_controller.create_inbox

# send an email from the inbox
inbox_controller.send_email(inbox.id, {
    send_email_options: {
        to: ["test@example.org"],
        subject: "Test",
        isHTML: true,
        body: <<-HEREDOC
          <p>MailSlurp supports HTML</p>

You can also use objects for most method options:

opts = {
  send_email_options: MailSlurpClient::SendEmailOptions.new(
      to: [inbox_2.email_address],
      subject: 'Test email',
      from: inbox_1.email_address,
      body: 'Test email content',
      is_html: true,
      attachments: attachment_ids
inbox_controller.send_email(inbox_1.id, opts)

Send with SMTP

    require 'net/smtp'
    access_details = inbox_controller.get_imap_smtp_access(inbox_id: inbox.id)
      address= access_details.secure_smtp_server_host,
      port= access_details.secure_smtp_server_port,
      helo= inbox.email_address.match(/@(.+)/)[1],
      user= access_details.secure_smtp_username,
      secret= access_details.secure_smtp_password,
      authtype= :plain
    ) do |smtp|
      message = <<EOF
Subject: SMTP test

This is my body
      smtp.send_message message, inbox.email_address, inbox.email_address

Receive emails

To read already existing emails use the Email Controller. To wait for expected emails to arrive use the WaitFor Controller. You can use MailSlurp to wait for at least 1 unread email in an inbox and return it. If a timeout is exceeded it will throw an error instead:

wait_for_controller = MailSlurpClient::WaitForControllerApi.new
wait_options = {
  inbox_id: inbox.id,
  timeout: 120000,
  unread_only: true
email = wait_for_controller.wait_for_latest_email(wait_options)
assert_match /Welcome/, email.body

Extract email content

code = email.body.match(/Your code is: ([0-9]{6})/)[1]
assert_equal code, '123456'

To parse an email and extract content use regex patterns like so:

wait_controller = MailSlurpClient::WaitForControllerApi.new
email = wait_controller.wait_for_latest_email({ inbox_id: inbox.id, unread_only: true, timeout: 30_000 })

# assert the email is a confirmation 
expect(email.subject).to include("Please confirm your email address")

# extract a 6 digit code from the email body
match = email.body.match(/code is ([0-9]{6})/)
if match == nil then
  raise "Could not find match in body #{email.body}"
code, * = match.captures


You can send attachments by first uploading files with the AttachmentControllerApi then using the returned attachment IDs in the send email method.

MailSlurp endpoints use base64 string encoding for upload and download files. To encode or decode strings in Ruby make sure you use the strict variables that avoid added newlines.

Upload and send

# upload a file to mailslurp to use as attachment
# @return [Array<String>]
def upload_file
# read a file to upload
data = File.open(PATH_TO_ATTACHMENT).read

# encode the data as base64 string (must be strict to avoid ruby adding new line characters)
encoded = Base64.strict_encode64(data)

attachment_controller = MailSlurpClient::AttachmentControllerApi.new
upload_options = MailSlurpClient::UploadAttachmentOptions.new(
    base64_contents: encoded,
    content_type: 'text/plain',
    filename: 'attachment.txt'

# return list of attachment ids

To send attachments

attachment_ids = upload_file

opts = {
  send_email_options: MailSlurpClient::SendEmailOptions.new(
      to: [inbox_2.email_address],
      subject: 'Test email',
      from: inbox_1.email_address,
      body: 'Test email content',
      is_html: true,
      attachments: attachment_ids
inbox_controller.send_email(inbox_1.id, opts)

Download received attachments

 # wait for the email to arrive (or fetch directly using email controller if you know it is there)
wait_opts = {
  inbox_id: inbox_2.id,
  timeout: 30_000,
  unread_only: true
email = wait_controller.wait_for_latest_email(wait_opts)

# find the attachments on the email object
expect(email.attachments.size).to be(1)

# download the attachment as base64 (easier than byte arrays for ruby client)
email_controller = MailSlurpClient::EmailControllerApi.new
downloaded_attachment = email_controller.download_attachment_base64(email.attachments[0], email.id)

# extract attachment content
expect(downloaded_attachment.content_type).to eq("text/plain")
expect(downloaded_attachment.size_bytes).to be_truthy
expect(downloaded_attachment.base64_file_contents).to be_truthy


Send email between two inboxes

It is common to use MailSlurp in test environments. Here is an example RSpec test:

require 'mailslurp_client'

# read mailslurp api key from environment variables

describe 'use MailSlurp ruby sdk to create email addresses then send and receive email' do
  before(:all) do
    expect(API_KEY).to be_truthy

    # configure mailslurp with API key
    MailSlurpClient.configure do |config|
      config.api_key['x-api-key'] = API_KEY

  it 'can an inbox with an email address' do
    # create a new email address
    inbox_controller = MailSlurpClient::InboxControllerApi.new
    inbox = inbox_controller.create_inbox

    # has a mailslurp email address
    expect(inbox.id).to be_truthy
    expect(inbox.email_address).to include('@mailslurp.com')

  it 'can send and receive emails' do
    inbox_controller = MailSlurpClient::InboxControllerApi.new
    wait_controller  = MailSlurpClient::WaitForControllerApi.new

    # create two inboxes
    inbox_1 = inbox_controller.create_inbox
    inbox_2 = inbox_controller.create_inbox

    # send email from inbox 1 to inbox 2 (you can send emails to any address)
    # for send options see https://ruby.mailslurp.com/MailSlurpClient/SendEmailOptions.html
    opts = {
      send_email_options: MailSlurpClient::SendEmailOptions.new(
          to: [inbox_2.email_address],
          subject: 'Test email',
          from: inbox_1.email_address,
          body: 'Test email content',
          is_html: true
    inbox_controller.send_email(inbox_1.id, opts)

    expect(inbox_2.id).to be_truthy

    # now wait for the email to arrive
    wait_opts = {
      inbox_id: inbox_2.id,
      timeout: 30_000,
      unread_only: true
    email = wait_controller.wait_for_latest_email(wait_opts)
    expect(email.body).to include('Test email content')

SDK Documentation

See the examples page or the full Method Documentation on Github.