diff --git a/app/mailers/spree/base_mailer.rb b/app/mailers/spree/base_mailer.rb
index 5d6e616b1f..d0f86d8ace 100644
--- a/app/mailers/spree/base_mailer.rb
+++ b/app/mailers/spree/base_mailer.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Spree
   class BaseMailer < ActionMailer::Base
     # Inline stylesheets
diff --git a/app/mailers/spree/order_mailer.rb b/app/mailers/spree/order_mailer.rb
index cb90f25b68..4cd6676c59 100644
--- a/app/mailers/spree/order_mailer.rb
+++ b/app/mailers/spree/order_mailer.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Spree
   class OrderMailer < BaseMailer
     helper HtmlHelper
diff --git a/app/mailers/spree/shipment_mailer.rb b/app/mailers/spree/shipment_mailer.rb
index d9f00671a1..ccbac24efe 100644
--- a/app/mailers/spree/shipment_mailer.rb
+++ b/app/mailers/spree/shipment_mailer.rb
@@ -1,9 +1,12 @@
+# frozen_string_literal: true
+
 module Spree
   class ShipmentMailer < BaseMailer
     def shipped_email(shipment, resend = false)
       @shipment = shipment.respond_to?(:id) ? shipment : Spree::Shipment.find(shipment)
       subject = (resend ? "[#{Spree.t(:resend).upcase}] " : '')
-      subject += "#{Spree::Config[:site_name]} #{Spree.t('shipment_mailer.shipped_email.subject')} ##{@shipment.order.number}"
+      base_subject = Spree.t('shipment_mailer.shipped_email.subject')
+      subject += "#{Spree::Config[:site_name]} #{base_subject} ##{@shipment.order.number}"
       mail(to: @shipment.order.email, from: from_address, subject: subject)
     end
   end
diff --git a/app/mailers/spree/test_mailer.rb b/app/mailers/spree/test_mailer.rb
index 8a54742722..1f41f55a52 100644
--- a/app/mailers/spree/test_mailer.rb
+++ b/app/mailers/spree/test_mailer.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Spree
   class TestMailer < BaseMailer
     def test_email(user)
diff --git a/spec/mailers/order_mailer_spec.rb b/spec/mailers/order_mailer_spec.rb
index 3af2b50339..2261edc802 100644
--- a/spec/mailers/order_mailer_spec.rb
+++ b/spec/mailers/order_mailer_spec.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'spec_helper'
 
 describe Spree::OrderMailer do
@@ -6,12 +8,12 @@ describe Spree::OrderMailer do
   contect "original spree specs" do
     let(:order) do
       order = stub_model(Spree::Order)
-      product = stub_model(Spree::Product, :name => %Q{The "BEST" product})
-      variant = stub_model(Spree::Variant, :product => product)
-      price = stub_model(Spree::Price, :variant => variant, :amount => 5.00)
-      line_item = stub_model(Spree::LineItem, :variant => variant, :order => order, :quantity => 1, :price => 4.99)
-      variant.stub(:default_price => price)
-      order.stub(:line_items => [line_item])
+      product = stub_model(Spree::Product, name: %{The "BEST" product})
+      variant = stub_model(Spree::Variant, product: product)
+      price = stub_model(Spree::Price, variant: variant, amount: 5.00)
+      line_item = stub_model(Spree::LineItem, variant: variant, order: order, quantity: 1, price: 4.99)
+      variant.stub(default_price: price)
+      order.stub(line_items: [line_item])
       order
     end
 
@@ -44,15 +46,15 @@ describe Spree::OrderMailer do
     context "only shows eligible adjustments in emails" do
       before do
         order.adjustments.create(
-          :label    => "Eligible Adjustment",
-          :amount   => 10,
-          :eligible => true
+          label: "Eligible Adjustment",
+          amount: 10,
+          eligible: true
         )
 
         order.adjustments.create!(
-          :label    => "Ineligible Adjustment",
-          :amount   => -10,
-          :eligible => false
+          label: "Ineligible Adjustment",
+          amount: -10,
+          eligible: false
         )
       end
 
@@ -85,8 +87,8 @@ describe Spree::OrderMailer do
     context "emails must be translatable" do
       context "pt-BR locale" do
         before do
-          pt_br_confirm_mail = { :spree => { :order_mailer => { :confirm_email => { :dear_customer => 'Caro Cliente,' } } } }
-          pt_br_cancel_mail = { :spree => { :order_mailer => { :cancel_email => { :order_summary_canceled => 'Resumo da Pedido [CANCELADA]' } } } }
+          pt_br_confirm_mail = { spree: { order_mailer: { confirm_email: { dear_customer: 'Caro Cliente,' } } } }
+          pt_br_cancel_mail = { spree: { order_mailer: { cancel_email: { order_summary_canceled: 'Resumo da Pedido [CANCELADA]' } } } }
           I18n.backend.store_translations :'pt-BR', pt_br_confirm_mail
           I18n.backend.store_translations :'pt-BR', pt_br_cancel_mail
           I18n.locale = :'pt-BR'
diff --git a/spec/mailers/shipment_mailer_spec.rb b/spec/mailers/shipment_mailer_spec.rb
index c7a0da6172..994ec0b871 100644
--- a/spec/mailers/shipment_mailer_spec.rb
+++ b/spec/mailers/shipment_mailer_spec.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'spec_helper'
 require 'email_spec'
 
@@ -7,12 +9,12 @@ describe Spree::ShipmentMailer do
 
   let(:shipment) do
     order = stub_model(Spree::Order)
-    product = stub_model(Spree::Product, :name => %Q{The "BEST" product})
-    variant = stub_model(Spree::Variant, :product => product)
-    line_item = stub_model(Spree::LineItem, :variant => variant, :order => order, :quantity => 1, :price => 5)
+    product = stub_model(Spree::Product, name: %{The "BEST" product})
+    variant = stub_model(Spree::Variant, product: product)
+    line_item = stub_model(Spree::LineItem, variant: variant, order: order, quantity: 1, price: 5)
     shipment = stub_model(Spree::Shipment)
-    shipment.stub(:line_items => [line_item], :order => order)
-    shipment.stub(:tracking_url => "TRACK_ME")
+    shipment.stub(line_items: [line_item], order: order)
+    shipment.stub(tracking_url: "TRACK_ME")
     shipment
   end
 
@@ -26,7 +28,7 @@ describe Spree::ShipmentMailer do
   # Regression test for #2196
   it "doesn't include out of stock in the email body" do
     shipment_email = Spree::ShipmentMailer.shipped_email(shipment)
-    shipment_email.body.should_not include(%Q{Out of Stock})
+    shipment_email.body.should_not include(%{Out of Stock})
   end
 
   it "shipment_email accepts an shipment id as an alternative to an Shipment object" do
@@ -40,7 +42,9 @@ describe Spree::ShipmentMailer do
     context "shipped_email" do
       context "pt-BR locale" do
         before do
-          pt_br_shipped_email = { :spree => { :shipment_mailer => { :shipped_email => { :dear_customer => 'Caro Cliente,' } } } }
+          pt_br_shipped_email = {
+            spree: { shipment_mailer: { shipped_email: { dear_customer: 'Caro Cliente,' } } }
+          }
           I18n.backend.store_translations :'pt-BR', pt_br_shipped_email
           I18n.locale = :'pt-BR'
         end
diff --git a/spec/mailers/test_mailer_spec.rb b/spec/mailers/test_mailer_spec.rb
index 6ed147ad10..b758040547 100644
--- a/spec/mailers/test_mailer_spec.rb
+++ b/spec/mailers/test_mailer_spec.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'spec_helper'
 require 'email_spec'
 
@@ -20,4 +22,4 @@ describe Spree::TestMailer do
       test_email = Spree::TestMailer.test_email(user.id)
     }.should_not raise_error
   end
-end
\ No newline at end of file
+end