Why is Hotmail still tagging my email as spam?

==== Required information ====
- iRedMail version (check /etc/iredmail-release): iRedmail 0.9.2
- Linux/BSD distribution name and version: Debian 7
- Store mail accounts in which backend (LDAP/MySQL/PGSQL): MySQL
- Web server (Apache or Nginx): Nginx
- Manage mail accounts with iRedAdmin-Pro? No
- Related log if you're reporting an issue:
====

Hi.
I'm having a problem with my emails which are sent to hotmail accounts. According to mail-tester.com I have 10/10 score so I don't know why Hotmail tags my emails as spam. Mail-tester only warns me due to the rDNS (PTR) points to different domain (vps.anotherdomain.pl) but I've solved this and now reverse lookup tools show the correct FQDN (Don't know why mail-tester still warns about this).

The headers of my emails are

Received: from mymachine.mydomain.com ([myIP]) by COL004-MC3F30.hotmail.com over TLS secured channel with Microsoft SMTPSVC(7.5.7601.23008);
     Wed, 8 Jul 2015 00:52:06 -0700
Received: from mymachine.mydomain.com (localhost.localdomain [127.0.0.1])
    by mymachine.mydomain.com (Postfix) with ESMTP id 578DE82BF5
    for <someone@hotmail.com>; Wed,  8 Jul 2015 03:52:05 -0400 (EDT)
Authentication-Results: mymachine.mydomain.com (amavisd-new);
    dkim=pass (1024-bit key) reason="pass (just generated, assumed good)"
    header.d=mydomain.com

Btw, this line

Received: from mymachine.mydomain.com (localhost.localdomain [127.0.0.1])

shouldn't be like?

Received: from mymachine.mydomain.com (mymachine.mydomain.com [myIP])

Thanks in advance!