diff --git a/app/mailers/user_notifications.rb b/app/mailers/user_notifications.rb
index 9192ea6e7..218247690 100644
--- a/app/mailers/user_notifications.rb
+++ b/app/mailers/user_notifications.rb
@@ -127,7 +127,7 @@ class UserNotifications < ActionMailer::Base
       title: post.topic.title,
       post: post,
       username: post.user.username,
-      from_alias: SiteSetting.enable_email_names ? post.user.name : post.user.username,
+      from_alias: (SiteSetting.enable_email_names && !post.user.name.empty?) ? post.user.name : post.user.username,
       allow_reply_by_email: true,
       use_site_subject: true,
       add_re_to_subject: true,
@@ -173,7 +173,7 @@ class UserNotifications < ActionMailer::Base
 
     user_name = @notification.data_hash[:original_username]
     if @post && SiteSetting.enable_email_names
-      user_name = User.find_by(id: @post.user_id).name
+      user_name = User.find_by(id: @post.user_id).name if !User.find_by(id: @post.user_id).name.empty?
     end
 
     notification_type = opts[:notification_type] || Notification.types[@notification.notification_type].to_s
diff --git a/spec/mailers/user_notifications_spec.rb b/spec/mailers/user_notifications_spec.rb
index a8ddc4246..fa03d5ac7 100644
--- a/spec/mailers/user_notifications_spec.rb
+++ b/spec/mailers/user_notifications_spec.rb
@@ -131,11 +131,11 @@ describe UserNotifications do
   end
 
   describe '.user_posted' do
-    let(:response_by_user) { Fabricate(:user, name: "John Doe") }
+    let(:response_by_user) { Fabricate(:user, name: "John Doe", username: "john") }
     let(:post) { Fabricate(:post) }
     let(:response) { Fabricate(:post, topic: post.topic, user: response_by_user)}
     let(:user) { Fabricate(:user) }
-    let(:notification) { Fabricate(:notification, user: user) }
+    let(:notification) { Fabricate(:notification, user: user, data: {original_username: response_by_user.username}.to_json) }
 
     it 'generates a correct email' do
       SiteSetting.stubs(:enable_email_names).returns(false)
@@ -144,6 +144,9 @@ describe UserNotifications do
       # from should not include full user name if "show user full names" is disabled
       expect(mail[:from].display_names).to_not eql(['John Doe'])
 
+      # from should include username if "show user full names" is disabled
+      expect(mail[:from].display_names).to eql(['john'])
+
       # subject should not include category name
       expect(mail.subject).not_to match(/Uncategorized/)
 
@@ -160,18 +163,18 @@ describe UserNotifications do
   end
 
   describe '.user_private_message' do
-    let(:response_by_user) { Fabricate(:user, name: "John Doe") }
+    let(:response_by_user) { Fabricate(:user, name: "", username: "john") }
     let(:topic) { Fabricate(:private_message_topic) }
     let(:response) { Fabricate(:post, topic: topic, user: response_by_user)}
     let(:user) { Fabricate(:user) }
-    let(:notification) { Fabricate(:notification, user: user) }
+    let(:notification) { Fabricate(:notification, user: user, data: {original_username: response_by_user.username}.to_json) }
 
     it 'generates a correct email' do
       SiteSetting.stubs(:enable_email_names).returns(true)
       mail = UserNotifications.user_private_message(response.user, post: response, notification: notification)
 
-      # from should include full user name
-      expect(mail[:from].display_names).to eql(['John Doe'])
+      # from should include username if full user name is not provided
+      expect(mail[:from].display_names).to eql(['john'])
 
       # subject should include "[PM]"
       expect(mail.subject).to match("[PM]")