如何删除邮件头中的发件人主机名

how do i change example.com to localhost in mail header. I am using ubuntu postfix server and swift mailer for sending mails.

Received: from localhost (example.com. [12.12..121])
    by mx.google.com with ESMTP id s22si1128306qge.14.2016.04.06.00.17.45
    for <............@gmail.com>;
    Wed, 06 Apr 2016 00:17:45 -0700 (PDT)

Thanks

You may try to use directly the FQDN (exemple.com) of your mail sending host instead of "localhost" when specifying your Swift_???Transport either directly (Smtp), or via the command line arguments of you mail command (Sendmail).