How to Send Transactional Emails with AWS SES in Rails (No Dependencies)

I previously wrote about integrating AWS SES with Rails using the aws-sdk-rails gem. While that approach works fine, I've since discovered an even simpler method - you don't need any AWS SDK gems at all. Rails' built-in SMTP support works perfectly with SES.

Hat tip to Justin Searls' excellent post on this topic, which I stumbled upon while researching this.

Step 1: Configure Production (AWS SES via SMTP)

Open config/environments/production.rb and add the SMTP configuration:

# config/environments/production.rb

Rails.application.configure do
  # ... existing config ...

  config.action_mailer.delivery_method = :smtp
  config.action_mailer.smtp_settings = {
    # Will vary by region (e.g. "email-smtp.us-east-1.amazonaws.com")
    address: ENV["AWS_SMTP_ENDPOINT"],
    # Create an SMTP user: https://docs.aws.amazon.com/ses/latest/dg/smtp-credentials.html
    user_name: ENV["AWS_SMTP_USERNAME"],
    password: ENV["AWS_SMTP_PASSWORD"],
    # Encrypt via STARTTLS. See: https://docs.aws.amazon.com/ses/latest/dg/smtp-connect.html
    enable_starttls: true,
    port: 587,
    # :login authentication encodes the password in base64
    authentication: :login
  }
end

Step 2: Get Your SMTP Credentials from AWS

Unlike the AWS SDK approach, SMTP credentials are different from your regular IAM access keys.

1. Go to the AWS Console and navigate to Amazon SES.
2. In the left sidebar, click SMTP settings.
3. Note your SMTP endpoint (e.g., email-smtp.eu-central-1.amazonaws.com).
4. Click Create SMTP credentials.
5. This creates a special IAM user for SMTP. Give it a name like ses-smtp-user.
6. Download or copy the SMTP username and password immediately - you won't see the password again!

Step 3: Add Environment Variables

Add these to your production environment (Heroku, Railway, or your server):

AWS_SMTP_ENDPOINT=email-smtp.eu-central-1.amazonaws.com
AWS_SMTP_USERNAME=AKIA...............
AWS_SMTP_PASSWORD=BK9E...........................

Step 4: Configure Local Development

For local development, you don't want to send real emails. Use letter_opener to preview emails in your browser instead.

First, add the gem to your Gemfile:

# Gemfile

group :development do
  # Preview email in the browser instead of sending
  gem "letter_opener"
end

Run the installation:

bundle install

Then configure your development environment in config/environments/development.rb:

# config/environments/development.rb

Rails.application.configure do
  # ... existing config ...

  # Use letter_opener to preview emails in browser
  config.action_mailer.delivery_method = :letter_opener
  config.action_mailer.perform_deliveries = true
  config.action_mailer.raise_delivery_errors = true
end

Now when you send an email in development, it will automatically open in your browser instead of being sent.

Step 5: Update Your Mailer

Make sure your mailers use a verified domain or email address:

# app/mailers/application_mailer.rb
class ApplicationMailer < ActionMailer::Base
  default from: "[email protected]" # Must be verified in SES
  layout "mailer"
end

Testing in Production (Rails Console)

Once deployed, you can test from the Rails console:

ActionMailer::Base.mail(
  from: "[email protected]",
  to: "[email protected]",
  subject: "Hello from Rails & SES",
  body: "This is a test email sent via AWS SES SMTP."
).deliver_now

If it returns a <Mail::Message> object without errors, check your inbox!

Why SMTP Instead of the SDK?

• No additional dependencies - Uses Rails' built-in SMTP support
• Simpler configuration - Just environment variables, no gem setup
• Easier debugging - Standard SMTP errors are well-documented
• Works everywhere - Any hosting platform that allows outbound SMTP

Important Notes

1. SES Sandbox: New SES accounts start in sandbox mode. You can only send to verified email addresses until you request production access.

2. Verify your domain: Go to SES > Verified identities and add your domain. You'll need to add DNS records to prove ownership.

3. SMTP credentials are NOT IAM credentials: The SMTP username/password are specifically generated for SMTP access and are different from your regular AWS access keys.

4. Regional endpoints: Make sure your SMTP endpoint matches the region where you verified your domain.