> ## 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 with Rails > Learn how to send your first email using Rails and the Resend Ruby SDK. ## Prerequisites Before you start, you'll need: * A Resend [API key](/create-an-api-key) * A [verified domain](/add-a-domain) ## Guide Get the Resend Ruby SDK. ```bash RubyGems theme={"theme":{"light":"github-light","dark":"vesper"}} gem install resend ``` ```bash Gemfile theme={"theme":{"light":"github-light","dark":"vesper"}} gem 'resend' ``` This gem can be used as an Action Mailer delivery method. First, let's update or create your mailer initializer file with your Resend API Key. ```rb config/initializers/mailer.rb theme={"theme":{"light":"github-light","dark":"vesper"}} Resend.api_key = "re_xxxxxxxxx" ``` 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 = :resend ``` 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 Full Rails web application Basic email sending Send emails with file attachments Send emails using Resend hosted templates Schedule emails for future delivery Manage contacts and audiences Create and manage sending domains Receive and process inbound emails Double opt-in subscription flow