FIX: support incoming emails with no subject

config/locales/server.en.yml

@@ -47,6 +47,10 @@ en:
   disable_remote_images_download_reason: "Remote images download was disabled because there wasn't enough disk space available."
   anonymous: "Anonymous"
 
+  emails:
+    incoming:
+      default_subject: "Incoming email from %{email}"
+
   errors: &errors
     format: ! '%{attribute} %{message}'
     messages:

lib/email/receiver.rb

@@ -40,7 +40,7 @@ module Email
     def find_or_create_incoming_email
       IncomingEmail.find_or_create_by(message_id: @mail.message_id) do |incoming_email|
         incoming_email.raw = @raw_email
-        incoming_email.subject = @mail.subject
+        incoming_email.subject = subject
         incoming_email.from_address = @mail.from.first.downcase
         incoming_email.to_addresses = @mail.to.map(&:downcase).join(";") if @mail.to.present?
         incoming_email.cc_addresses = @mail.cc.map(&:downcase).join(";") if @mail.cc.present?
@@ -60,7 +60,7 @@ module Email
 
       raise InactiveUserError if !user.active && !user.staged
 
-      if action = subscription_action_for(body, @mail.subject)
+      if action = subscription_action_for(body, subject)
         message = SubscriptionMailer.send(action, user)
         Email::Sender.new(message, :subscription).send
       elsif post = find_related_post
@@ -73,14 +73,14 @@ module Email
         case destination[:type]
         when :group
           group = destination[:obj]
-          create_topic(user: user, raw: body, title: @mail.subject, archetype: Archetype.private_message, target_group_names: [group.name], skip_validations: true)
+          create_topic(user: user, raw: body, title: subject, archetype: Archetype.private_message, target_group_names: [group.name], skip_validations: true)
         when :category
           category = destination[:obj]
 
           raise StrangersNotAllowedError    if user.staged? && !category.email_in_allow_strangers
           raise InsufficientTrustLevelError if !user.has_trust_level?(SiteSetting.email_in_min_trust)
 
-          create_topic(user: user, raw: body, title: @mail.subject, category: category.id)
+          create_topic(user: user, raw: body, title: subject, category: category.id)
         when :reply
           email_log = destination[:obj]
 
@@ -156,6 +156,10 @@ module Email
       @from ||= @mail[:from].address_list.addresses.first
     end
 
+    def subject
+      @suject ||= @mail.subject.presence || I18n.t("emails.incoming.default_subject", email: @mail.from.first.downcase)
+    end
+
     def find_or_create_user(address_field)
       # decode the address field
       address_field.decoded

spec/components/email/receiver_spec.rb

@@ -219,6 +219,7 @@ describe Email::Receiver do
       expect { process(:encoded_display_name) }.to change(Topic, :count)
 
       topic = Topic.last
+      expect(topic.title).to eq("I need help")
       expect(topic.private_message?).to eq(true)
       expect(topic.allowed_groups).to include(group)
 
@@ -228,6 +229,11 @@ describe Email::Receiver do
       expect(user.name).to eq("Случайная Имя")
     end
 
+    it "handles email with no subject" do
+      expect { process(:no_subject) }.to change(Topic, :count)
+      expect(Topic.last.title).to eq("Incoming email from some@one.com")
+    end
+
     it "invites everyone in the chain but emails configured as 'incoming' (via reply, group or category)" do
       expect { process(:cc) }.to change(Topic, :count)
       emails = Topic.last.allowed_users.pluck(:email)

spec/fixtures/emails/no_subject.eml

@@ -0,0 +1,9 @@
+From: Some One <some@one.com>
+To: team@bar.com
+Date: Mon, 1 Feb 2016 00:12:43 +0100
+Message-ID: <40@foo.bar.mail>
+Mime-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: quoted-printable
+
+This is an email with no subject...