diff --git a/script/import_scripts/mbox.rb b/script/import_scripts/mbox.rb
index d47b5553f..3ff41e945 100755
--- a/script/import_scripts/mbox.rb
+++ b/script/import_scripts/mbox.rb
@@ -37,6 +37,7 @@ class ImportScripts::Mbox < ImportScripts::Base
     topics = []
 
     topic_lookup = {}
+    topic_titles = {}
     replies = []
 
     all_messages do |mail, filename|
@@ -44,21 +45,55 @@ class ImportScripts::Mbox < ImportScripts::Base
 
       msg_id = mail['Message-ID'].to_s
       reply_to = mail['In-Reply-To'].to_s
+      title = clean_title(mail['Subject'].to_s)
 
       if reply_to.present?
         topic = topic_lookup[reply_to] || reply_to
         topic_lookup[msg_id] = topic
-        replies << {id: msg_id, topic: topic, file: filename}
+        replies << {id: msg_id, topic: topic, file: filename, title: title}
       else
-        topics << {id: msg_id, file: filename}
+        topics << {id: msg_id, file: filename, title: title}
+	topic_titles[title] ||= msg_id
       end
     end
 
+    # Replies without parents should be hoisted to topics
+    to_hoist = []
+    replies.each do |r|
+      to_hoist << r if !topic_lookup[r[:topic]]
+    end
+
+    to_hoist.each do |h|
+      replies.delete(h)
+      topics << {id: h[:id], file: h[:file], title: h[:title]}
+      topic_titles[h[:title]] ||= h[:id]
+    end
+
+    # Topics with duplicate replies should be replies
+    to_group = []
+    topics.each do |t|
+      first = topic_titles[t[:title]]
+      to_group << t if first && first != t[:id]
+    end
+
+    to_group.each do |t|
+      topics.delete(t)
+      replies << {id: t[:id], topic: topic_titles[t[:title]], file: t[:file], title: t[:title]}
+    end
+
     File.write(USER_INDEX_PATH, {users: users}.to_json)
     File.write(TOPIC_INDEX_PATH, {topics: topics}.to_json)
     File.write(REPLY_INDEX_PATH, {replies: replies}.to_json)
   end
 
+  def clean_title(title)
+    title.gsub(/^Re: */i, '')
+  end
+
+  def clean_raw(raw)
+    raw.gsub(/-- \nYou received this message because you are subscribed to the Google Groups "[^"]*" group.\nTo unsubscribe from this group and stop receiving emails from it, send an email to [^+@]+\+unsubscribe@googlegroups.com\.\nFor more options, visit https:\/\/groups\.google\.com\/groups\/opt_out\./, '')
+  end
+
   def import_users
     puts "", "importing users"
 
@@ -100,7 +135,7 @@ class ImportScripts::Mbox < ImportScripts::Base
       topics = all_topics[offset..offset+BATCH_SIZE-1]
       break if topics.nil?
 
-      next if all_records_exist? :posts, topics.map {|t| t['id'].to_i}
+      next if all_records_exist? :posts, topics.map {|t| t['id']}
 
       create_posts(topics, total: topic_count, offset: offset) do |t|
         raw_email = File.read(t['file'])
@@ -116,11 +151,11 @@ class ImportScripts::Mbox < ImportScripts::Base
         title = mail.subject.gsub(/\[[^\]]+\]+/, '').strip
 
         { id: t['id'],
-          title: title,
+          title: clean_title(title),
           user_id: user_id_from_imported_user_id(mail.from.first) || Discourse::SYSTEM_USER_ID,
           created_at: mail.date,
           category: CATEGORY_ID,
-          raw: raw,
+          raw: clean_raw(raw),
           cook_method: Post.cook_methods[:email] }
       end
     end
@@ -129,9 +164,6 @@ class ImportScripts::Mbox < ImportScripts::Base
   def import_replies
     puts "", "creating topic replies"
 
-    all_topics = ::JSON.parse(File.read(TOPIC_INDEX_PATH))['topics']
-    topic_count = all_topics.size
-
     replies = ::JSON.parse(File.read(REPLY_INDEX_PATH))['replies']
     post_count = replies.size
 
@@ -139,7 +171,7 @@ class ImportScripts::Mbox < ImportScripts::Base
       posts = replies[offset..offset+BATCH_SIZE-1]
       break if posts.nil?
 
-      next if all_records_exist? :posts, posts.map {|p| p['id'].to_i}
+      next if all_records_exist? :posts, posts.map {|p| p['id']}
 
       create_posts(posts, total: post_count, offset: offset) do |p|
         parent_id = p['topic']
@@ -161,7 +193,7 @@ class ImportScripts::Mbox < ImportScripts::Base
           topic_id: topic_id,
           user_id: user_id_from_imported_user_id(mail.from.first) || Discourse::SYSTEM_USER_ID,
           created_at: mail.date,
-          raw: raw,
+          raw: clean_raw(raw),
           cook_method: Post.cook_methods[:email] }
       end
     end