Action Mailer setup in Ruby on Rails

Introduction

Action Mailer helps your Rails app send emails easily. It organizes email sending like writing and sending letters.

Send welcome emails when users sign up.

Notify users about password changes.

Send order confirmations in an online store.

Deliver newsletters or updates to subscribers.

Syntax

Ruby on Rails

class UserMailer < ApplicationMailer
  default from: '[e-mail]'

  def welcome_email(user)
    @user = user
    mail(to: @user.email, subject: 'Welcome to My Awesome Site')
  end
end

Define a mailer class inheriting from ApplicationMailer.

Use mail method to set recipient and subject.

Examples

A simple mailer method sending an alert email.

Ruby on Rails

class NotificationMailer < ApplicationMailer
  def alert_email(user)
    mail(to: user.email, subject: 'Alert!')
  end
end

Sets a default sender email for all mails in this mailer.

Ruby on Rails

class UserMailer < ApplicationMailer
  default from: '[e-mail]'

  def reset_password_email(user)
    @user = user
    mail(to: @user.email, subject: 'Reset your password')
  end
end

Sample Program

This example shows how to set up SMTP settings in development, create a mailer, and send a welcome email immediately.

Ruby on Rails

# config/environments/development.rb
Rails.application.configure do
  config.action_mailer.delivery_method = :smtp
  config.action_mailer.smtp_settings = {
    address: 'smtp.example.com',
    port: 587,
    user_name: '[e-mail]',
    password: 'password',
    authentication: :plain,
    enable_starttls_auto: true
  }
end

# app/mailers/user_mailer.rb
class UserMailer < ApplicationMailer
  default from: '[e-mail]'

  def welcome_email(user)
    @user = user
    mail(to: @user.email, subject: 'Welcome to My Awesome Site')
  end
end

# Usage in Rails console or controller
user = OpenStruct.new(email: '[e-mail]')
email = UserMailer.welcome_email(user)
email.deliver_now

puts "Email sent to: #{email.to.first} with subject: '#{email.subject}'"

Important Notes

Remember to configure SMTP settings for your environment to send emails.

Use deliver_now to send immediately or deliver_later to send asynchronously.

Test emails in development with tools like Letter Opener or Mailcatcher to avoid sending real emails.

Summary

Action Mailer organizes email sending in Rails apps.

Define mailer classes and methods to create emails.

Configure SMTP settings to send emails through a mail server.

Practice

1. What is the main purpose of Action Mailer in a Rails application?

easy

A. To manage database migrations automatically

B. To send emails by defining mailer classes and methods

C. To handle user authentication and sessions

D. To style HTML views with CSS

Solution

1. Step 1: Understand Action Mailer role

   Action Mailer is designed to send emails by organizing mailer classes and methods.

2. Step 2: Compare with other Rails features

   Database migrations, authentication, and styling are handled by other parts of Rails, not Action Mailer.

3. Final Answer:

   To send emails by defining mailer classes and methods -> Option B

4. Quick Check:

   Action Mailer = send emails [OK]

Hint: Remember: Action Mailer is for emails, not database or styling [OK]

Common Mistakes:

• Confusing Action Mailer with Active Record migrations
• Thinking it handles user login or CSS styling
• Assuming it manages background jobs directly

2. Which of the following is the correct way to define a mailer method in a Rails mailer class?

easy

A. def welcome_email(user) mail to: user.email, subject: 'Welcome' end

B. def welcome_email(user) { send_email(to: user.email) }

C. def welcome_email(user) mail(to user.email, subject 'Welcome') end

D. def welcome_email(user); mail(to: user.email, subject: 'Welcome'); end

Solution

1. Step 1: Check Ruby method syntax

   Method definitions use def name(params); ...; end with parentheses and semicolons optional but recommended for clarity.

2. Step 2: Verify mail method usage

   The mail method requires keyword arguments with colons, e.g., to: user.email, and commas between arguments.

3. Final Answer:

   def welcome_email(user); mail(to: user.email, subject: 'Welcome'); end -> Option D

4. Quick Check:

   Correct Ruby method and mail syntax = def welcome_email(user); mail(to: user.email, subject: 'Welcome'); end [OK]

Hint: Use parentheses and colons for keyword args in mail method [OK]

Common Mistakes:

• Missing parentheses or commas in method definition
• Using braces {} instead of do...end or semicolons
• Omitting colons in keyword arguments

3. Given this mailer method in Rails:

class UserMailer < ApplicationMailer
  def notify(user)
    mail(to: user.email, subject: 'Notice')
  end
end

What will happen when you call UserMailer.notify(user).deliver_now?

medium

A. An email is sent immediately to the user's email address

B. An email is queued but not sent until later

C. A syntax error occurs because deliver_now is invalid

D. Nothing happens because notify method lacks a body

Solution

1. Step 1: Understand deliver_now behavior

   The deliver_now method sends the email immediately when called on a mail object.

2. Step 2: Check mailer method correctness

   The notify method calls mail with valid parameters, so it returns a mail object ready to send.

3. Final Answer:

   An email is sent immediately to the user's email address -> Option A

4. Quick Check:

   deliver_now sends email immediately = An email is sent immediately to the user's email address [OK]

Hint: deliver_now sends email immediately, deliver_later queues it [OK]

Common Mistakes:

• Confusing deliver_now with deliver_later
• Thinking mail method sends email by itself
• Assuming notify method must have email body text

4. You wrote this mailer method:

def alert(user)
  mail(to: user.email, subject: 'Alert')
end

But emails are not sending. Which is the most likely cause?

medium

A. SMTP settings are not configured properly in environment files

B. The mail method is missing a block with email body content

C. You forgot to call deliver_now or deliver_later

D. Mailer class must inherit from ActionMailer::Base explicitly

Solution

1. Step 1: Check SMTP configuration

   Without proper SMTP settings, emails cannot be sent even if mailer code is correct.

2. Step 2: Review other options

   Mailer inheritance from ApplicationMailer is standard; mail method can use templates for body; calling deliver_now is needed but question implies method is called.

3. Final Answer:

   SMTP settings are not configured properly in environment files -> Option A

4. Quick Check:

   SMTP config missing = emails not sent [OK]

Hint: Check SMTP setup first if emails don't send [OK]

Common Mistakes:

• Assuming mail method sends email without deliver_now
• Forgetting to configure SMTP in config/environments
• Thinking mailer must inherit directly from ActionMailer::Base

5. You want to configure Action Mailer to send emails via Gmail SMTP in production. Which configuration snippet in config/environments/production.rb is correct?

hard

A. config.action_mailer.smtp_settings = { address: 'smtp.gmail.com', port: 587, domain: 'gmail.com', user_name: ENV['GMAIL_USERNAME'], password: ENV['GMAIL_PASSWORD'], authentication: 'plain' }

B. config.action_mailer.smtp_settings = { address: 'smtp.gmail.com', port: 25, domain: 'gmail.com', user_name: 'user', password: 'pass', authentication: 'login', enable_ssl: true }

C. config.action_mailer.smtp_settings = { address: 'smtp.gmail.com', port: 587, domain: 'yourdomain.com', user_name: ENV['GMAIL_USERNAME'], password: ENV['GMAIL_PASSWORD'], authentication: 'plain', enable_starttls_auto: true }

D. config.action_mailer.smtp_settings = { address: 'smtp.gmail.com', port: 465, domain: 'yourdomain.com', user_name: ENV['GMAIL_USERNAME'], password: ENV['GMAIL_PASSWORD'], authentication: 'plain', enable_starttls_auto: false }

Solution

1. Step 1: Identify correct SMTP port and security

   Gmail SMTP uses port 587 with STARTTLS enabled (enable_starttls_auto: true) for secure email sending.

2. Step 2: Check domain and authentication

   Domain should be your app's domain, authentication 'plain' is standard, and credentials should come from environment variables for security.

3. Final Answer:

   config.action_mailer.smtp_settings = { address: 'smtp.gmail.com', port: 587, domain: 'yourdomain.com', user_name: ENV['GMAIL_USERNAME'], password: ENV['GMAIL_PASSWORD'], authentication: 'plain', enable_starttls_auto: true } -> Option C

4. Quick Check:

   Gmail SMTP with port 587 and STARTTLS = config.action_mailer.smtp_settings = { address: 'smtp.gmail.com', port: 587, domain: 'yourdomain.com', user_name: ENV['GMAIL_USERNAME'], password: ENV['GMAIL_PASSWORD'], authentication: 'plain', enable_starttls_auto: true } [OK]

Hint: Use port 587 and enable_starttls_auto true for Gmail SMTP [OK]

Common Mistakes:

• Using wrong port like 25 or 465 without proper TLS
• Setting domain to 'gmail.com' instead of your app domain
• Omitting enable_starttls_auto or setting it false