Merge pull request #483 in ZP/z-push from bugfix/ZP-1172-some-mails-bodies-or-headers-in-japanese to develop

* commit 'ae1e82f0':
  ZP-1172 Some mails bodies or headers in Japanese may be decoded in wrong encoding. Released under the Affero GNU General Public License (AGPL) version 3.
  ZP-1172 Some mails bodies or headers in Japanese may be decoded in wrong encoding. Released under the Affero GNU General Public License (AGPL) version 3.
  ZP-1172 Some mails bodies or headers in Japanese may be decoded in wrong encoding. Released under the Affero GNU General Public License (AGPL) version 3.
  ZP-1172 Some mails bodies or headers in Japanese may be decoded in wrong encoding. Released under the Affero GNU General Public License (AGPL) version 3.