add sample mailer

app/mailers/sample_mailer.rb

@@ -0,0 +1,13 @@
+class SampleMailer < ApplicationMailer
+
+  # Subject can be set in your I18n file at config/locales/en.yml
+  # with the following lookup:
+  #
+  #   en.sample_mailer.hello.subject
+  #
+  def hello
+    @greeting = "Hi"
+
+    mail to: "to@example.org"
+  end
+end

app/views/sample_mailer/hello.html.erb

@@ -0,0 +1,5 @@
+<h1>Sample#hello</h1>
+
+<p>
+  <%= @greeting %>, find me in app/views/sample_mailer/hello.html.erb
+</p>

app/views/sample_mailer/hello.text.erb

@@ -0,0 +1,3 @@
+Sample#hello
+
+<%= @greeting %>, find me in app/views/sample_mailer/hello.text.erb

test/mailers/previews/sample_mailer_preview.rb

@@ -0,0 +1,9 @@
+# Preview all emails at http://localhost:3000/rails/mailers/sample_mailer
+class SampleMailerPreview < ActionMailer::Preview
+
+  # Preview this email at http://localhost:3000/rails/mailers/sample_mailer/hello
+  def hello
+    SampleMailer.hello
+  end
+
+end

test/mailers/sample_mailer_test.rb

@@ -0,0 +1,12 @@
+require "test_helper"
+
+class SampleMailerTest < ActionMailer::TestCase
+  test "hello" do
+    mail = SampleMailer.hello
+    assert_equal "Hello", mail.subject
+    assert_equal ["to@example.org"], mail.to
+    assert_equal ["from@example.com"], mail.from
+    assert_match "Hi", mail.body.encoded
+  end
+
+end