#3368 - Japanese character is garbled

app/models/channel/email_parser.rb

@@ -940,10 +940,21 @@ process unprocessable_mails (tmp/unprocessable_mail/*.eml) again
   # specific email needs to be forced to ISO-2022-JP
   # but that breaks other emails that can be forced to SJIS only
   # thus force to ISO-2022-JP but fallback to SJIS
+  #
+  # https://github.com/zammad/zammad/issues/3368
+  # some characters are not included in the official ISO-2022-JP
+  # ISO-2022-JP-KDDI superset provides support for more characters
   def force_japanese_encoding(input)
-    input.force_encoding('ISO-2022-JP').encode('UTF-8')
+    %w[ISO-2022-JP ISO-2022-JP-KDDI SJIS]
+      .lazy
+      .map { |encoding| try_encoding(input, encoding) }
+      .detect(&:present?)
+  end
+
+  def try_encoding(input, encoding)
+    input.force_encoding(encoding).encode('UTF-8')
   rescue
-    input.force_encoding('SJIS').encode('UTF-8')
+    nil
   end
 end
 

test/data/mail/mail099.box

@@ -0,0 +1,13 @@
+Content-Type: text/plain; charset=ISO-2022-JP
+Content-Transfer-Encoding: 7bit
+From: "example"
+ <noreply@example.org>
+Reply-To: info@example.org
+Errors-To: return@example.org
+To: noreply@example.org
+Subject: example
+Message-Id: <msgid@example.org>
+Date: Fri, 1 Jan 2021 10:00:00 +0900 (JST)
+
+$B!!!!!!!!!!-!#1ET#38)$N03$H!"(B
+

test/data/mail/mail099.yml

@@ -0,0 +1,10 @@
+--- !ruby/hash:ActiveSupport::HashWithIndifferentAccess
+from: example <noreply@example.org>
+from_email: noreply@example.org
+from_display_name: example
+to: noreply@example.org
+subject: example
+body: "　　　　　①１都３県の鯵と、\n\n"
+content_type: text/plain
+reply-to: info@example.org
+attachments: []