> ## Documentation Index > Fetch the complete documentation index at: https://resend.com/docs/llms.txt > Use this file to discover all available pages before exploring further. # Send emails using Rails with SMTP > Learn how to integrate Rails with Resend SMTP. ## Prerequisites Before you start, you'll need: * A Resend [API key](/create-an-api-key) * A [verified domain](/add-a-domain) ## Guide Add these lines of code into your environment config file. ```rb config/environments/environment.rb theme={"theme":{"light":"github-light","dark":"vesper"}} config.action_mailer.delivery_method = :smtp config.action_mailer.smtp_settings = { :address => 'smtp.resend.com', :port => 465, :user_name => 'resend', :password => ENV['RESEND_API_KEY'], :tls => true } ``` Then create a `UserMailer` class definition. ```rb app/mailers/user_mailer.rb theme={"theme":{"light":"github-light","dark":"vesper"}} class UserMailer < ApplicationMailer default from: 'Acme ' # this domain must be verified with Resend def welcome_email @user = params[:user] @url = 'http://example.com/login' mail(to: ["delivered@resend.dev"], subject: 'hello world') end end ``` And create your ERB email template. ```html app/views/user_mailer/welcome_email.html.erb theme={"theme":{"light":"github-light","dark":"vesper"}}

Welcome to example.com, <%= @user.name %>

You have successfully signed up to example.com,

To log in to the site, just follow this link: <%= @url %>.

Thanks for joining and have a great day!

``` Initialize your `UserMailer` class. This returns an `ActionMailer::MessageDelivery` instance. ```rb theme={"theme":{"light":"github-light","dark":"vesper"}} u = User.new name: "derich" mailer = UserMailer.with(user: u).welcome_email # => #, @processed_mailer=...> ``` Finally, you can now send emails using the `deliver_now!` method: ```rb theme={"theme":{"light":"github-light","dark":"vesper"}} mailer.deliver_now! # => {:id=>"a193c81e-9ac5-4708-a569-5caf14220539", :from=>....} ``` ## Examples See the full source code.