> ## 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)
## 1. Install
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'
```
## 2. Send email using Rails Action Mailer
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 should return a `UserMailer` instance.
```rb theme={"theme":{"light":"github-light","dark":"vesper"}}
u = User.new name: "derich"
mailer = UserMailer.with(user: u).welcome_email
# => #, , , ...
```
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=>....}
```
## 3. Try it yourself
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