🔲Resend

This guide outlines how to install and configure the Resend Gem for sending transactional emails in your Lightning Rails project.

Step 1: Create a Resend Account

1. Go to the Resend website.

2. Sign up and create an account to access your API key.

---

Step 2: Add the Resend Gem

1. Open your Gemfile.

2. Add the Resend gem in your Gemfile:

   gem "resend"

3. Run bundle install in your terminal to install the gem.

   bundle install

---

Step 3: Configure Your API Key

1. Locate your API key from the Resend dashboard.

2. Add the API key to your .env file:

   RESEND_API_KEY="re_***************"

3. Ensure you have the .env file setup as specified in the quickstart guide.

---

Step 4: Set Up Action Mailer

1. Development Environment: Open config/environments/development.rb and set the delivery method to :letter_opener for testing emails locally (The Gem is already installed in the boilerplate):

   config.action_mailer.delivery_method = :letter_opener

2. Production Environment delivery method: Open config/environments/production.rb and set the delivery method to :resend:

   config.action_mailer.delivery_method = :resend

3. API key in production

   1. Create a new initializer file: touch app/config/initializers/mailer.rb

   2. Paste your API key, and make sure your API key is set in your hosting provider:

      Resend.api_key = ENV["RESEND_API_KEY"]

---

(Optional) Welcome Email

Step 5: Create Your First Mailer

1. Generate a new mailer:

   rails generate mailer UserMailer

2. Open the newly created file app/mailers/user_mailer.rb and define a mailer method. For example:

   class UserMailer < ApplicationMailer
     def welcome_email
       @user = params[:user]
       mail(to: @user.email, subject: "Welcome to Our App!")
     end
   end

---

Step 6: Add HTML Content for the Email

1. Create a corresponding view file for the mailer:

touch app/views/user_mailer/welcome_email.html.erb

• Path: app/views/user_mailer/welcome_email.html.erb

• Content example:

  <h1>Welcome to Our App, <%= @user.name %>!</h1>
  <p>We’re excited to have you on board.</p>

---

Step 7: Initialize and Send the Mailer

1. Open the Rails console:

   rails console

2. Initialize the mailer with a sample user object:

   u = User.new(name: "Derich", email: "[e-mail]")
   mailer = UserMailer.with(user: u).welcome_email

3. Send the email:

   mailer.deliver_now!

4. Add an auto-welcome message to welcome your users in user.rb

class User < ApplicationRecord
# [...]
  after_create :send_welcome_email

  def send_welcome_email
    UserMailer.with(user: self).welcome_email.deliver_now
  end
end

---

Step 8: Verify the Email

• Check the recipient's inbox to confirm the email has been sent successfully.

• If testing in development, verify the email opens correctly using the letter_opener gem.

---

That's it! You’ve successfully set up the Resend Gem for sending transactional an marketing emails in your Lightning Rails project, you can enjoy 100 free emails per month.