Merge pull request #539 in ZP/z-push from bugfix/ZP-1226-sent-mails-to-or-cc-field-may-be to develop

* commit '7fe8135b':
  ZP-1226 Sent mails' To or Cc field may be junk string at other mail clients. Released under the Affero GNU General Public License (AGPL) version 3.