Mailcow mail server: mail goes in spam

I set up a mail server with mailcow on my Debian vserver. host- and mailname is mail.DOMAIN.de . I set up the DNS records like MX and SPF too. you can see all my records here :

there is nothing showy in the mail header:

Delivered-To: RECEIVER@gmail.com
Received: by 10.200.37.154 with SMTP id e26csp1028322qte;
        Mon, 26 Jun 2017 06:13:43 -0700 (PDT)
X-Received: by 10.223.161.149 with SMTP id u21mr14521713wru.70.1498482823112;
        Mon, 26 Jun 2017 06:13:43 -0700 (PDT)
ARC-Seal: i=1; a=rsa-sha256; t=1498482823; cv=none;
        d=google.com; s=arc-20160816;
        b=Yylk3JtaULCZZ884shkY4PdhX3LR7XRlN5qpyaUg13lMIZTBVrTesuV4ypHbJNI3XX
         kRD04fRvCAWcrAKiIp0qkSSzNXgdN67cQNI/GA/cv62swSnisv5uZ7e+WBVtIRdCPKXX
         sLTMzlpBGQWdcNMqcukIpeVda5J5HdT2+LqadLuaZYKVOMMEhXaleM2ha3hmWCprYgXX
         7mRiAmZzEvncDZFRs/JItBtdYb28zjwKxUpChYO+aZbM1DUyFqSf5izydeBCElYTdMXX
         kq3DE4UZCf2641T4aPXFADomOh/DvHEKUzL0Au1J6MkD9EdyTda+sz+Zly56VFsAx5XX
         hlaw==
ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816;
        h=content-language:content-transfer-encoding:mime-version:date
         :message-id:subject:from:to:arc-authentication-results;
        bh=g3zLYH4xKxcPrHOD18z9YfpQcnk/GaJedfustWU5uXX=;
        b=I6KJbX6O2e58u8DerN+HvZL2OvgkLm+5kWpFBLmy/XM22GRY/nQ0b8XGwQTnJjjWXX
         RwNXMzt+DGY6hOhNdRzJtQuDZr+j8f5nQKQshkeYu00+i8Dje/oJBflf8LqwjsgRL5XX
         /dMIcl9leS9ug52izVt8+J3VXygLnCw8umPoYpGkiEgh6BG/alZFvxk+UnnaB4oBxTXX
         WKEzfeIcReEOmXPmvQRmEyAsS/VqbwPAWV4y4XcxVPaM7bIIDOtl4jKNhx0sMMXX+sI/
         ei1pQ2nY7QYF2Y4QLbpG+veLmB+omIIzP0ZnmSUtHl6xJDVvXq/gE5/csdWXPeypVMXX
         byGQ==
ARC-Authentication-Results: i=1; mx.google.com;
       spf=pass (google.com: best guess record for domain of mail@DOMAIN.de designates XXX.XX.X.180 as permitted sender) smtp.mailfrom=Mail@DOMAIN.de
Return-Path: <Mail@DOMAIN.de>
Received: from mail.DOMAIN.de (mail.DOMAIN.de. [XXX.XX.X.180])
        by mx.google.com with ESMTPS id w34si11726441wrc.389.2017.06.26.06.13.42
        for <RECEIVER@gmail.com>
        (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128);
        Mon, 26 Jun 2017 06:13:43 -0700 (PDT)
Received-SPF: pass (google.com: best guess record for domain of mail@DOMAIN.de designates XXX.XX.X.180 as permitted sender) client-ip=XXX.XX.X.180;
Authentication-Results: mx.google.com;
       spf=pass (google.com: best guess record for domain of mail@DOMAIN.de designates XXX.XX.X.180 as permitted sender) smtp.mailfrom=Mail@DOMAIN.de
Received: from [127.0.0.1] (localhost [127.0.0.1])
    by mail.DOMAIN.de (Postfix) with ESMTP id 75E1A61029
    for <RECEIVER@gmail.com>; Mon, 26 Jun 2017 15:13:40 +0200 (CEST)
X-Fuglu-Suspect: 83acc7dd2821431f80c1537e1036333b
X-Fuglu-Spamstatus: NO
X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on mail.DOMAIN.de
X-Spam-Status: No, score=-1.0 required=5.0 tests=ALL_TRUSTED autolearn=ham
    autolearn_force=no
Received: from [127.0.0.1] (localhost [127.0.0.1])
    (Authenticated sender: mail@DOMAIN.de)
    by mail.DOMAIN.de (Postfix) with ESMTPSA
    for <RECEIVER@gmail.com>; Mon, 26 Jun 2017 15:13:40 +0200 (CEST)

if I send a mail to Gmail it goes to spam, at GMX.de not in spam… but why in spam with Gmail ??