Ruby on Rails

Transactional emails with Loops simplify your code. With our WYSIWYG editor and API-like payloads, you can design and manage email templates outside of your codebase, ensuring cleaner code and easier template maintenance.

Unlike older SMTP services, Loops requires the body of emails sent via SMTP to be formatted as an API-like payload. This approach allows you to use Loops’ powerful email editor to craft your emails and keep email templating outside of your application code.

Every email sent over Loops SMTP requires a transactional email to be set up in your Loops account. Note the transactionalId value in the email payload.

Here’s how you can set up transactional emails with Loops SMTP in Rails:

Create emails in Loops

Create transactional emails in Loops using the editor.Add data variables to your emails for any dynamic content you want to send from your Rails application.

Configure Action Mailer

To use Loops SMTP, configure Action Mailer using the following settings.

The password value should be an API key from your API Settings page.

config/environments/production.rb

config.action_mailer.delivery_method = :smtp
config.action_mailer.smtp_settings = {
  address:         'smtp.loops.so',
  port:            587,
  user_name:       'loops',
  password:        '<API_KEY>',
  authentication:  'plain',
  enable_starttls: true
}

Send emails from Rails

Now you can send emails from your application.Here’s an example Mailer:

app/mailers/user_mailer.rb

class UserMailer < ApplicationMailer

  def login_email
    @user = params[:user]
    # Note: the "to" address is required by Action Mailer
    #  but is overwritten by the email provided in the view
    #  (see below). Likewise, a subject is not required here
    #  because Loops will use the subject provided in the editor.
    mail(to: @user.email)
  end

end

Loops’ SMTP system doesn’t send full HTML emails directly. Instead, you should provide a structured API-like payload, which Loops will then use to render an HTML email.Create a text view for your email, like below.You can copy an example payload from the Publish page of your transactional email in Loops.

app/views/user_mailer/login_email.text.erb

{
  "transactionalId": "clomzp89u635xl30px7wrl0ri",
  "email": "<%= @user.email %>", /* recipient */
  "dataVariables": {
    "loginUrl": "https://myapp.com/login?code=<%= @user.auth_code %>"
  }
}

You do not need to provide an HTML view for your emails when using Loops SMTP (i.e.: login_email.html.erb is not required).

Send transactional email

Read how to send transactional email with our API.

Transactional email guide

Learn how to send transactional email with Loops.

Last modified on June 23, 2026

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