FIX: email replies to closed topic should not be accepted

lib/email/receiver.rb

@@ -15,6 +15,7 @@ module Email
     class UserNotFoundError < ProcessingError; end
     class UserNotSufficientTrustLevelError < ProcessingError; end
     class BadDestinationAddress < ProcessingError; end
+    class TopicClosedError < ProcessingError; end
     class EmailLogNotFound < ProcessingError; end
     class InvalidPost < ProcessingError; end
 
@@ -68,6 +69,7 @@ module Email
         @email_log = dest_info[:obj]
 
         raise EmailLogNotFound if @email_log.blank?
+        raise TopicClosedError if Topic.find_by_id(@email_log.topic_id).closed?
 
         create_reply
       end