diff --git a/app/mailers/kudo_mailer.rb b/app/mailers/kudo_mailer.rb
index f47d34fddb9..6c210c32027 100644
--- a/app/mailers/kudo_mailer.rb
+++ b/app/mailers/kudo_mailer.rb
@@ -10,20 +10,18 @@ def batch_kudo_notification(user_id, user_kudos)
     user = User.find(user_id)
     kudos_hash = JSON.parse(user_kudos)
 
-    I18n.with_locale(user.preference.locale.iso) do
-      kudos_hash.each_pair do |commentable_info, kudo_givers_hash|
-        # Parse the key to extract the type and id of the commentable so we can
-        # weed out any commentables that no longer exist.
-        commentable_type, commentable_id = commentable_info.split("_")
-        commentable = commentable_type.constantize.find_by(id: commentable_id)
-        next unless commentable
+    kudos_hash.each_pair do |commentable_info, _kudo_givers_hash|
+      # Parse the key to extract the type and id of the commentable so we can
+      # weed out any commentables that no longer exist.
+      commentable_type, commentable_id = commentable_info.split("_")
+      commentable = commentable_type.constantize.find_by(id: commentable_id)
+      next unless commentable
 
-        @commentables << commentable
-      end
-      mail(
-        to: user.email,
-        subject: default_i18n_subject(app_name: ArchiveConfig.APP_SHORT_NAME)
-      )
+      @commentables << commentable
     end
+    mail(
+      to: user.email,
+      subject: default_i18n_subject(app_name: ArchiveConfig.APP_SHORT_NAME)
+    )
   end
 end
diff --git a/app/models/redis_mail_queue.rb b/app/models/redis_mail_queue.rb
index cd4d0958325..63a23045480 100644
--- a/app/models/redis_mail_queue.rb
+++ b/app/models/redis_mail_queue.rb
@@ -37,7 +37,9 @@ def self.deliver_kudos
       # queue the notification for delivery
       begin
         # don't die if we hit one deleted user
-        KudoMailer.batch_kudo_notification(author_id, user_kudos.to_json).deliver_later
+        I18n.with_locale(User.find(author_id).preference.locale.iso) do
+          KudoMailer.batch_kudo_notification(author_id, user_kudos.to_json).deliver_later
+        end
       rescue
       end
     end
diff --git a/app/views/kudo_mailer/batch_kudo_notification.html.erb b/app/views/kudo_mailer/batch_kudo_notification.html.erb
index 97b1776b1bd..3dded0b680d 100644
--- a/app/views/kudo_mailer/batch_kudo_notification.html.erb
+++ b/app/views/kudo_mailer/batch_kudo_notification.html.erb
@@ -12,13 +12,13 @@
       # kudos are present.
       givers = names.dup
       givers << t(".guest", count: guest_count) unless guest_count.zero?
-      givers_list = givers.map { |k| style_bold(k) }.to_sentence.html_safe
+      givers_list = to_sentence(givers.map { |k| style_bold(k) })
     %>
 
     <% if kudo_count == 1 && guest_count == 1 %>
-      <%= t(".html.single_guest.left_kudos", giver_list: style_bold(t(".html.single_guest.giver_list")).html_safe, commentable_link: commentable_link.html_safe).html_safe %>
+      <%= t(".single_guest.html", giver: style_bold(t(".single_guest.giver")), commentable_link: commentable_link) %>
     <% else %>
-      <%= t(".html.left_kudos", givers_list: givers_list, commentable_link: commentable_link.html_safe, count: kudo_count).html_safe %>
+      <%= t(".left_kudos.html", givers_list: givers_list, commentable_link: commentable_link, count: kudo_count) %>
     <% end %>
 
     <% if (index < @commentables.length - 1) %>
diff --git a/app/views/kudo_mailer/batch_kudo_notification.text.erb b/app/views/kudo_mailer/batch_kudo_notification.text.erb
index dd56a2c9415..a79104b9649 100644
--- a/app/views/kudo_mailer/batch_kudo_notification.text.erb
+++ b/app/views/kudo_mailer/batch_kudo_notification.text.erb
@@ -12,13 +12,13 @@
   # present.
   givers = names.dup
   givers << t(".guest", count: guest_count) unless guest_count.zero?
-  givers_list = givers.to_sentence
+  givers_list = to_sentence(givers)
 %>
 
 <% if kudo_count == 1 && guest_count == 1 %>
-<%= t(".text.single_guest", commentable_title: commentable_title, commentable_url: commentable_url) %>
+<%= t(".single_guest.text", commentable_title: commentable_title, commentable_url: commentable_url) %>
 <% else %>
-<%= t(".text.left_kudos", givers_list: givers_list, commentable_title: commentable_title, commentable_url: commentable_url, count: kudo_count) %>
+<%= t(".left_kudos.text", givers_list: givers_list, commentable_title: commentable_title, commentable_url: commentable_url, count: kudo_count) %>
 <% end %>
 
 <% if (index < @commentables.length - 1) %>
diff --git a/config/locales/mailers/en.yml b/config/locales/mailers/en.yml
index 84c9570101f..78269dd98d2 100644
--- a/config/locales/mailers/en.yml
+++ b/config/locales/mailers/en.yml
@@ -31,19 +31,18 @@ en:
       guest:
         one: a guest
         other: "%{count} guests"
-      html:
-        left_kudos:
+      left_kudos:
+        html:
           one: "%{givers_list} left kudos on %{commentable_link}."
           other: "%{givers_list} left kudos on %{commentable_link}."
-        single_guest:
-          giver_list: A guest
-          left_kudos: "%{giver_list} left kudos on %{commentable_link}."
-      subject: "[%{app_name}] You've got kudos!"
-      text:
-        left_kudos:
+        text:
           one: '%{givers_list} left kudos on "%{commentable_title}" (%{commentable_url}).'
           other: '%{givers_list} left kudos on "%{commentable_title}" (%{commentable_url}).'
-        single_guest: A guest left kudos on "%{commentable_title}" (%{commentable_url}).
+      single_guest:
+        giver: A guest
+        html: "%{giver} left kudos on %{commentable_link}."
+        text: A guest left kudos on "%{commentable_title}" (%{commentable_url}).
+      subject: "[%{app_name}] You've got kudos!"
   mailer:
     general:
       closing:
diff --git a/features/comments_and_kudos/kudos.feature b/features/comments_and_kudos/kudos.feature
index c6f85220ce1..6361c32603f 100644
--- a/features/comments_and_kudos/kudos.feature
+++ b/features/comments_and_kudos/kudos.feature
@@ -168,6 +168,32 @@ Feature: Kudos
       And the email should not contain "0 guests"
       And the email should not contain "translation missing"
 
+  Scenario: Translated kudos email
+
+    Given a locale with translated emails
+      And the user "myname1" enables translated emails
+      And all emails have been delivered
+      And the kudos queue is cleared
+      And I am logged in as "myname2"
+      And I leave kudos on "Awesome Story"
+    When kudos are sent
+    Then 1 email should be delivered to "myname1@foo.com"
+      And the email should have "Translated subject" in the subject
+      And the email to "myname1" should contain "myname2"
+      And the email to "myname1" should contain "Awesome Story"
+      And the email to "myname1" should be translated
+    # AO3-6042: Emails should not obey user's locale preference when locales are deactivated
+    When the locale preference feature flag is disabled for user "myname1"
+      And all emails have been delivered
+      And I am logged in as "myname3"
+      And I leave kudos on "Awesome Story"
+      And kudos are sent
+    Then 1 email should be delivered to "myname1@foo.com"
+      And the email should have "You've got kudos!" in the subject
+      And the email to "myname1" should contain "myname3"
+      And the email to "myname1" should contain "Awesome Story"
+      And the email to "myname1" should be non-translated
+
   Scenario: Blocked users should not see a kudos button on their blocker's works
     Given the work "Aftermath" by "creator"
       And the user "creator" has blocked the user "pest"
diff --git a/features/step_definitions/email_custom_steps.rb b/features/step_definitions/email_custom_steps.rb
index baec4b83c4b..3bc384a72ef 100644
--- a/features/step_definitions/email_custom_steps.rb
+++ b/features/step_definitions/email_custom_steps.rb
@@ -1,40 +1,70 @@
-Given /^(?:a clear email queue|no emails have been sent|the email queue is clear)$/ do
+Given "the email queue is clear" do
   reset_mailer
 end
 
-Then /^"([^\"]*)" should be emailed$/ do |user|
+Given "a locale with translated emails" do
+  FactoryBot.create(:locale, iso: "new")
+  # The footer keys are used in all emails
+  I18n.backend.store_translations(:new, { mailer: { general: { footer: { general: { about: { html: "Translated footer", text: "Translated footer" } } } } } })
+  I18n.backend.store_translations(:new, { kudo_mailer: { batch_kudo_notification: { subject: "Translated subject" } } })
+end
+
+Given "the user {string} enables translated emails" do |user|
+  user = User.find_by(login: user)
+  $rollout.activate_user(:set_locale_preference, user)
+  user.preference.update!(locale: Locale.find_by(iso: "new"))
+end
+
+Given "the locale preference feature flag is disabled for user {string}" do |user|
+  user = User.find_by(login: user)
+  $rollout.deactivate_user(:set_locale_preference, user)
+end
+
+Then "the email to {string} should be translated" do |user|
+  step(%{the email to "#{user}" should contain "Translated footer"})
+  step(%{the email to "#{user}" should not contain "fan-run and fan-supported archive"}) # untranslated English text
+  step(%{the email to "#{user}" should not contain "translation missing"}) # missing translations in the target language fall back to English
+end
+
+Then "the email to {string} should be non-translated" do |user|
+  step(%{the email to "#{user}" should not contain "Translated footer"})
+  step(%{the email to "#{user}" should contain "fan-run and fan-supported archive"})
+  step(%{the email to "#{user}" should not contain "translation missing"})
+end
+
+Then "{string} should be emailed" do |user|
   @user = User.find_by(login: user)
-  emails("to: \"#{email_for(@user.email)}\"").size.should > 0
+  expect(emails("to: \"#{email_for(@user.email)}\"")).not_to be_empty
 end
 
-Then /^"([^\"]*)" should not be emailed$/ do |user|
+Then "{string} should not be emailed" do |user|
   @user = User.find_by(login: user)
-  emails("to: \"#{email_for(@user.email)}\"").size.should == 0
+  expect(emails("to: \"#{email_for(@user.email)}\"")).to be_empty
 end
 
-Then /^the email to "([^\"]*)" should contain "([^\"]*)"$/ do |user, text|
+Then "the email to {string} should contain {string}" do |user, text|
   @user = User.find_by(login: user)
   email = emails("to: \"#{email_for(@user.email)}\"").first
   if email.multipart?
-    email.text_part.body.should =~ /#{text}/
-    email.html_part.body.should =~ /#{text}/
+    expect(email.text_part.body).to match(text)
+    expect(email.html_part.body).to match(text)
   else
-    email.body.should =~ /#{text}/
+    expect(email.body).to match(text)
   end
 end
 
-Then /^the email to "([^\"]*)" should not contain "([^\"]*)"$/ do |user, text|
+Then "the email to {string} should not contain {string}" do |user, text|
   @user = User.find_by(login: user)
   email = emails("to: \"#{email_for(@user.email)}\"").first
   if email.multipart?
-    email.text_part.body.should_not =~ /#{text}/
-    email.html_part.body.should_not =~ /#{text}/
+    expect(email.text_part.body).not_to match(text)
+    expect(email.html_part.body).not_to match(text)
   else
-    email.body.should_not =~ /#{text}/
+    expect(email.body).not_to match(text)
   end
 end
 
-Then(/^"([^\"]*)" should receive (\d+) emails?$/) do |user, count|
+Then "{string} should receive {int} email(s)" do |user, count|
   @user = User.find_by(login: user)
-  emails("to: \"#{email_for(@user.email)}\"").size.should == count.to_i
+  expect(emails("to: \"#{email_for(@user.email)}\"").size).to eq(count.to_i)
 end
diff --git a/spec/mailers/user_mailer_spec.rb b/spec/mailers/user_mailer_spec.rb
index 13324a80cd2..970b96f678e 100644
--- a/spec/mailers/user_mailer_spec.rb
+++ b/spec/mailers/user_mailer_spec.rb
@@ -1204,54 +1204,4 @@
       it_behaves_like "an email with a deleted work with draft chapters attached"
     end
   end
-
-  describe "obeys the set locale preference feature flag" do
-    let(:user) { create(:user) }
-    let(:work) { create(:work, authors: [user.default_pseud]) }
-    let(:locale) { create(:locale) }
-
-    context "when the set locale preference feature flag is on" do
-      before { $rollout.activate_user(:set_locale_preference, user) }
-
-      context "and the user has non-default locale set" do
-        before { user.preference.update!(locale: locale) }
-
-        it "sends a localised email" do
-          expect(I18n).to receive(:with_locale).with(locale.iso)
-          expect(UserMailer.admin_hidden_work_notification(work.id, user.id)).to be_truthy
-        end
-      end
-
-      context "and the user has the default locale set" do
-        before { user.preference.update!(locale: Locale.default) }
-
-        it "sends an English email" do
-          expect(I18n).to receive(:with_locale).with("en")
-          expect(UserMailer.admin_hidden_work_notification(work.id, user.id)).to be_truthy
-        end
-      end
-    end
-
-    context "when the set locale preference feature flag is off" do
-      before { $rollout.deactivate_user(:set_locale_preference, user) }
-
-      context "and the user has non-default locale set" do
-        before { user.preference.update!(locale: locale) }
-
-        it "sends an English email" do
-          expect(I18n).to receive(:with_locale).with("en")
-          expect(UserMailer.admin_hidden_work_notification(work.id, user.id)).to be_truthy
-        end
-      end
-
-      context "and the user has the default locale set" do
-        before { user.preference.update!(locale: Locale.default) }
-
-        it "sends an English email" do
-          expect(I18n).to receive(:with_locale).with("en")
-          expect(UserMailer.admin_hidden_work_notification(work.id, user.id)).to be_truthy
-        end
-      end
-    end
-  end
 end
diff --git a/test/mailers/previews/kudo_mailer_preview.rb b/test/mailers/previews/kudo_mailer_preview.rb
new file mode 100644
index 00000000000..f22588f5b05
--- /dev/null
+++ b/test/mailers/previews/kudo_mailer_preview.rb
@@ -0,0 +1,12 @@
+class KudoMailerPreview < ApplicationMailerPreview
+  # Sends a kudos notification
+  def batch_kudo_notification
+    user = create(:user)
+    work = create(:work)
+    guest_count = params[:guest_count] || 1
+    user_count = params[:user_count].to_i || 1
+    names = Array.new(user_count) { "User#{Faker::Alphanumeric.alpha(number: 8)}" }
+    hash = { "Work_#{work.id}": { guest_count:, names: } }
+    KudoMailer.batch_kudo_notification(user.id, hash.to_json)
+  end
+end