diff --git a/script/import_scripts/base.rb b/script/import_scripts/base.rb
index 3fcfce549a6..6a28124d3fa 100644
--- a/script/import_scripts/base.rb
+++ b/script/import_scripts/base.rb
@@ -458,7 +458,16 @@ class ImportScripts::Base
         .where("LOWER(name) = ?", opts[:name].downcase.strip)
         .first
 
-    return existing if existing
+    if existing
+      if import_id && existing.custom_fields["import_id"] != import_id
+        existing.custom_fields["import_id"] = import_id
+        existing.save!
+
+        add_category(import_id, existing)
+      end
+
+      return existing
+    end
 
     post_create_action = opts.delete(:post_create_action)
 
diff --git a/script/import_scripts/mbox/importer.rb b/script/import_scripts/mbox/importer.rb
index 71b405e7011..b3712481697 100644
--- a/script/import_scripts/mbox/importer.rb
+++ b/script/import_scripts/mbox/importer.rb
@@ -50,7 +50,8 @@ module ImportScripts::Mbox
       create_categories(rows) do |row|
         {
           id: row['name'],
-          name: row['name']
+          name: row['name'],
+          parent_category_id: row['parent_category_id'].presence,
         }
       end
     end
diff --git a/script/import_scripts/mbox/settings.yml b/script/import_scripts/mbox/settings.yml
index 4c0a3acc11a..639ee0fea33 100644
--- a/script/import_scripts/mbox/settings.yml
+++ b/script/import_scripts/mbox/settings.yml
@@ -48,4 +48,18 @@ tags:
 # https://en.wikipedia.org/wiki/List_of_email_subject_abbreviations#Abbreviations_in_other_languages).
 remove_subject_prefixes:
   - "Re: "
-  - "Fwd?: "
\ No newline at end of file
+  - "Fwd?: "
+
+# For emails processed by mailman with this type of bogus header:
+#   From: Jane Smith via ListName <ListName@lists.example.com>
+# attempt to get the actual sender's address from other available headers like Reply-To or the /^From / line
+fix_mailman_via_addresses: false
+
+# Elide up to last occurence of = in addresses (BATV, etc)
+# ie. normalize these:
+#     prvs=00377ab9a2=someone@somewhere.com
+#     bounces+840901-dbd9-flang-dev=someone@somewhere.com
+#     blah=blih=bluh=someone@somewhere.com
+# into:
+#     someone@somewhere.com
+elide_equals_in_addresses: false
diff --git a/script/import_scripts/mbox/support/database.rb b/script/import_scripts/mbox/support/database.rb
index 052f0d479a9..9eb0b1f30b1 100644
--- a/script/import_scripts/mbox/support/database.rb
+++ b/script/import_scripts/mbox/support/database.rb
@@ -30,8 +30,8 @@ module ImportScripts::Mbox
 
     def insert_category(category)
       @db.execute(<<-SQL, category)
-        INSERT OR REPLACE INTO category (name, description)
-        VALUES (:name, :description)
+        INSERT OR REPLACE INTO category (name, description, parent_category_id)
+        VALUES (:name, :description, :parent_category_id)
       SQL
     end
 
@@ -150,7 +150,7 @@ module ImportScripts::Mbox
 
     def fetch_categories
       @db.execute <<-SQL
-        SELECT name, description
+        SELECT name, description, parent_category_id
         FROM category
         ORDER BY name
       SQL
@@ -218,7 +218,8 @@ module ImportScripts::Mbox
       @db.execute <<-SQL
         CREATE TABLE IF NOT EXISTS category (
           name TEXT NOT NULL PRIMARY KEY,
-          description TEXT
+          description TEXT,
+          parent_category_id INTEGER
         )
       SQL
     end
diff --git a/script/import_scripts/mbox/support/indexer.rb b/script/import_scripts/mbox/support/indexer.rb
index c8164534d77..b381292c47a 100644
--- a/script/import_scripts/mbox/support/indexer.rb
+++ b/script/import_scripts/mbox/support/indexer.rb
@@ -55,7 +55,8 @@ module ImportScripts::Mbox
 
       category = {
         name: metadata['name'].presence || File.basename(directory),
-        description: metadata['description']
+        description: metadata['description'],
+        parent_category_id: metadata['parent_category_id'].presence,
       }
 
       @database.insert_category(category)
@@ -67,7 +68,28 @@ module ImportScripts::Mbox
         begin
           msg_id = receiver.message_id
           parsed_email = receiver.mail
+
           from_email, from_display_name = receiver.parse_from_field(parsed_email)
+
+          if @settings.fix_mailman_via_addresses
+            # Detect cases like this and attempt to get actual sender from other headers:
+            #    From: Jane Smith via ListName <ListName@lists.example.com>
+
+            if receiver.mail['X-Mailman-Version'] && from_display_name =~ /\bvia \S+$/i
+              email_from_from_line = opts[:from_line].scan(/From (\S+)/).flatten.first
+              a = Mail::Address.new(email_from_from_line)
+              from_email = a.address
+              from_display_name = a.display_name
+              # if name is not available there, look for it in Reply-To
+              if from_display_name.nil?
+                reply_to = receiver.mail.to_s.scan(/[\n\r]Reply-To: ([^\r\n]+)/).flatten.first
+                from_display_name = Mail::Address.new(reply_to).display_name
+              end
+            end
+          end
+
+          from_email = from_email.sub(/^(.*)=/, '') if @settings.elide_equals_in_addresses
+
           body, elided, format = receiver.select_body
           reply_message_ids = extract_reply_message_ids(parsed_email)
 
@@ -125,11 +147,12 @@ module ImportScripts::Mbox
         puts "indexing #{filename}"
 
         if @split_regex.present?
-          each_mail(filename) do |raw_message, first_line_number, last_line_number|
+          each_mail(filename) do |raw_message, first_line_number, last_line_number, from_line|
             opts = {
               first_line_number: first_line_number,
               last_line_number: last_line_number,
-              start_time: monotonic_time
+              start_time: monotonic_time,
+              from_line: from_line,
             }
             receiver = read_mail_from_string(raw_message)
             yield receiver, filename, opts if receiver.present?
@@ -159,13 +182,17 @@ module ImportScripts::Mbox
       first_line_number = 1
       last_line_number = 0
 
+      from_line = nil
+
       each_line(filename) do |line|
         if line.scrub =~ @split_regex
           if last_line_number > 0
-            yield raw_message, first_line_number, last_line_number
+            yield raw_message, first_line_number, last_line_number, from_line
             raw_message = +''
             first_line_number = last_line_number + 1
           end
+
+          from_line = line
         else
           raw_message << line
         end
@@ -173,7 +200,7 @@ module ImportScripts::Mbox
         last_line_number += 1
       end
 
-      yield raw_message, first_line_number, last_line_number if raw_message.present?
+      yield raw_message, first_line_number, last_line_number, from_line if raw_message.present?
     end
 
     def each_line(filename)
@@ -202,7 +229,7 @@ module ImportScripts::Mbox
 
     def extract_subject(receiver, list_name)
       subject = receiver.subject
-      subject.blank? ? nil : subject.strip
+      subject.blank? ? nil : subject.strip.gsub(/\t+/, ' ')
     end
 
     def ignored_file?(path, checksums)
diff --git a/script/import_scripts/mbox/support/settings.rb b/script/import_scripts/mbox/support/settings.rb
index e1fd15b8697..eff1511b67a 100644
--- a/script/import_scripts/mbox/support/settings.rb
+++ b/script/import_scripts/mbox/support/settings.rb
@@ -21,6 +21,8 @@ module ImportScripts::Mbox
     attr_reader :automatically_remove_list_name_prefix
     attr_reader :show_trimmed_content
     attr_reader :tags
+    attr_reader :fix_mailman_via_addresses
+    attr_reader :elide_equals_in_addresses
 
     def initialize(yaml)
       @data_dir = yaml['data_dir']
@@ -39,6 +41,8 @@ module ImportScripts::Mbox
 
       @automatically_remove_list_name_prefix = yaml['automatically_remove_list_name_prefix']
       @show_trimmed_content = yaml['show_trimmed_content']
+      @fix_mailman_via_addresses = yaml['fix_mailman_via_addresses']
+      @elide_equals_in_addresses = yaml['elide_equals_in_addresses']
 
       @tags = []
       if yaml['tags'].present?