diff --git a/app/views/notification_mailer/digest.text.erb b/app/views/notification_mailer/digest.text.erb
index 95aed6793..b63352978 100644
--- a/app/views/notification_mailer/digest.text.erb
+++ b/app/views/notification_mailer/digest.text.erb
@@ -1,6 +1,6 @@
 <%= display_name(@me) %>,
 
-<%= raw t('notification_mailer.digest.body', since: @since, instance: root_url) %>
+<%= raw t('notification_mailer.digest.body', since: l(@since), instance: root_url) %>
 <% @notifications.each do |notification| %>
 
 * <%= raw t('notification_mailer.digest.mention', name: notification.from_account.acct) %>
diff --git a/spec/mailers/notification_mailer_spec.rb b/spec/mailers/notification_mailer_spec.rb
index faa3197c8..811435606 100644
--- a/spec/mailers/notification_mailer_spec.rb
+++ b/spec/mailers/notification_mailer_spec.rb
@@ -3,13 +3,28 @@ require "rails_helper"
 RSpec.describe NotificationMailer, type: :mailer do
   let(:receiver)       { Fabricate(:user, account: Fabricate(:account, username: 'alice')) }
   let(:sender)         { Fabricate(:account, username: 'bob') }
-  let(:foreign_status) { Fabricate(:status, account: sender) }
-  let(:own_status)     { Fabricate(:status, account: receiver.account) }
+  let(:foreign_status) { Fabricate(:status, account: sender, text: 'The body of the foreign status') }
+  let(:own_status)     { Fabricate(:status, account: receiver.account, text: 'The body of the own status') }
+
+  shared_examples 'localized subject' do |*args, **kwrest|
+    it 'renders subject localized for the locale of the receiver' do
+      locale = I18n.available_locales.sample
+      receiver.update!(locale: locale)
+      expect(mail.subject).to eq I18n.t(*args, kwrest.merge(locale: locale))
+    end
+
+    it 'renders subject localized for the default locale if the locale of the receiver is unavailable' do
+      receiver.update!(locale: nil)
+      expect(mail.subject).to eq I18n.t(*args, kwrest.merge(locale: I18n.default_locale))
+    end
+  end
 
   describe "mention" do
     let(:mention) { Mention.create!(account: receiver.account, status: foreign_status) }
     let(:mail) { NotificationMailer.mention(receiver.account, Notification.create!(account: receiver.account, activity: mention)) }
 
+    include_examples 'localized subject', 'notification_mailer.mention.subject', name: 'bob'
+
     it "renders the headers" do
       expect(mail.subject).to eq("You were mentioned by bob")
       expect(mail.to).to eq([receiver.email])
@@ -17,6 +32,7 @@ RSpec.describe NotificationMailer, type: :mailer do
 
     it "renders the body" do
       expect(mail.body.encoded).to match("You were mentioned by bob")
+      expect(mail.body.encoded).to include 'The body of the foreign status'
     end
   end
 
@@ -24,6 +40,8 @@ RSpec.describe NotificationMailer, type: :mailer do
     let(:follow) { sender.follow!(receiver.account) }
     let(:mail) { NotificationMailer.follow(receiver.account, Notification.create!(account: receiver.account, activity: follow)) }
 
+    include_examples 'localized subject', 'notification_mailer.follow.subject', name: 'bob'
+
     it "renders the headers" do
       expect(mail.subject).to eq("bob is now following you")
       expect(mail.to).to eq([receiver.email])
@@ -38,6 +56,8 @@ RSpec.describe NotificationMailer, type: :mailer do
     let(:favourite) { Favourite.create!(account: sender, status: own_status) }
     let(:mail) { NotificationMailer.favourite(own_status.account, Notification.create!(account: receiver.account, activity: favourite)) }
 
+    include_examples 'localized subject', 'notification_mailer.favourite.subject', name: 'bob'
+
     it "renders the headers" do
       expect(mail.subject).to eq("bob favourited your status")
       expect(mail.to).to eq([receiver.email])
@@ -45,6 +65,7 @@ RSpec.describe NotificationMailer, type: :mailer do
 
     it "renders the body" do
       expect(mail.body.encoded).to match("Your status was favourited by bob")
+      expect(mail.body.encoded).to include 'The body of the own status'
     end
   end
 
@@ -52,6 +73,8 @@ RSpec.describe NotificationMailer, type: :mailer do
     let(:reblog) { Status.create!(account: sender, reblog: own_status) }
     let(:mail) { NotificationMailer.reblog(own_status.account, Notification.create!(account: receiver.account, activity: reblog)) }
 
+    include_examples 'localized subject', 'notification_mailer.reblog.subject', name: 'bob'
+
     it "renders the headers" do
       expect(mail.subject).to eq("bob boosted your status")
       expect(mail.to).to eq([receiver.email])
@@ -59,6 +82,7 @@ RSpec.describe NotificationMailer, type: :mailer do
 
     it "renders the body" do
       expect(mail.body.encoded).to match("Your status was boosted by bob")
+      expect(mail.body.encoded).to include 'The body of the own status'
     end
   end
 
@@ -66,6 +90,8 @@ RSpec.describe NotificationMailer, type: :mailer do
     let(:follow_request) { Fabricate(:follow_request, account: sender, target_account: receiver.account) }
     let(:mail) { NotificationMailer.follow_request(receiver.account, Notification.create!(account: receiver.account, activity: follow_request)) }
 
+    include_examples 'localized subject', 'notification_mailer.follow_request.subject', name: 'bob'
+
     it 'renders the headers' do
       expect(mail.subject).to eq('Pending follower: bob')
       expect(mail.to).to eq([receiver.email])
@@ -78,18 +104,44 @@ RSpec.describe NotificationMailer, type: :mailer do
 
   describe 'digest' do
     before do
-      mention = Fabricate(:mention, account: receiver.account)
+      mention = Fabricate(:mention, account: receiver.account, status: foreign_status)
       Fabricate(:notification, account: receiver.account, activity: mention)
+      sender.follow!(receiver.account)
     end
-    let(:mail) { NotificationMailer.digest(receiver.account, since: 5.days.ago) }
 
-    it 'renders the headers' do
-      expect(mail.subject).to match('notification since your last')
-      expect(mail.to).to eq([receiver.email])
+    context do
+      let!(:mail) { NotificationMailer.digest(receiver.account, since: 5.days.ago) }
+
+      include_examples 'localized subject', 'notification_mailer.digest.subject', count: 1, name: 'bob'
+
+      it 'renders the headers' do
+        expect(mail.subject).to match('notification since your last')
+        expect(mail.to).to eq([receiver.email])
+      end
+
+      it 'renders the body' do
+        expect(mail.body.encoded).to match('brief summary')
+        expect(mail.body.encoded).to include 'The body of the foreign status'
+        expect(mail.body.encoded).to include sender.username
+      end
     end
 
-    it 'renders the body' do
-      expect(mail.body.encoded).to match('brief summary')
+    it 'includes activities since the date specified by :since option' do
+      receiver.update!(last_emailed_at: '2000-02-01T00:00:00Z', current_sign_in_at: '2000-03-01T00:00:00Z')
+      mail = NotificationMailer.digest(receiver.account, since: Time.parse('2000-01-01T00:00:00Z'))
+      expect(mail.body.encoded).to include 'Jan 01, 2000, 00:00'
+    end
+
+    it 'includes activities since the receiver was last emailed if :since option is unavailable' do
+      receiver.update!(last_emailed_at: '2000-02-01T00:00:00Z', current_sign_in_at: '2000-03-01T00:00:00Z')
+      mail = NotificationMailer.digest(receiver.account)
+      expect(mail.body.encoded).to include 'Feb 01, 2000, 00:00'
+    end
+
+    it 'includes activities since the receiver last signed in if :since option and the last emailed date are unavailable' do
+      receiver.update!(last_emailed_at: nil, current_sign_in_at: '2000-03-01T00:00:00Z')
+      mail = NotificationMailer.digest(receiver.account)
+      expect(mail.body.encoded).to include 'Mar 01, 2000, 00:00'
     end
   end
 end