Use the authentication_token for finding the user

lib/gitlab/email/handler/create_issue.rb

@@ -11,7 +11,6 @@ module Gitlab
         def execute
           validate_permission!(:create_issue)
-          validate_authentication_token!
           verify_record(
             create_issue,
@@ -21,10 +20,7 @@ module Gitlab
         end
         def author
-          @author ||= mail.from.find do |email|
-            user = User.find_by_any_email(email)
-            break user if user
-          end
+          @author ||= User.find_by(authentication_token: authentication_token)
         end
         def project
@@ -48,11 +44,6 @@ module Gitlab
             description: message
           ).execute
         end
-
-        def validate_authentication_token!
-          raise UserNotAuthorizedError unless author.authentication_token ==
-                                                authentication_token
-        end
       end
     end
   end

spec/lib/gitlab/email/receiver_spec.rb

@@ -224,11 +224,11 @@ describe Gitlab::Email::Receiver, lib: true do
         end
       end
-      context "when the authentication_token token didn't match" do
+      context "when we can't find the authentication_token" do
         let!(:email_raw) { fixture_file("emails/wrong_authentication_token.eml") }
-        it "raises an UserNotAuthorizedError" do
-          expect { receiver.execute }.to raise_error(Gitlab::Email::UserNotAuthorizedError)
+        it "raises an UserNotFoundError" do
+          expect { receiver.execute }.to raise_error(Gitlab::Email::UserNotFoundError)
         end
       end