DKIM without BIND - Check OK, but nothing in mail header

I successfully setup DKIM (I mean no warning in Virtualmin) on a virtual server using remote DNS servers (using the given info). The documentation says it is not supported, but I did not see any problem to add the appropriate records in the external DNS servers (appart removing the double quotes and line feeds in the key). Actually, a check on https://www.mail-tester.com/spf-dkim-check is successfull (domain: web2.see.asso.fr, selector: 2015)

However, nothing goes out in emails. Example of an email sent from usermin:

Return-Path: diffusion@web2.see.asso.fr Delivered-To: j.vieille@controlchaingroup.com Received: from localhost (HELO queue) (127.0.0.1) by localhost with SMTP; 22 May 2016 16:05:39 +0200 Received: from web2.see.asso.fr (37.187.137.19) by mx1.ovh.net with SMTP; 22 May 2016 16:05:38 +0200 Received: from ns406606.ip-37-187-137.eu (localhost.localdomain [127.0.0.1]) by web2.see.asso.fr (Postfix) with SMTP id D174D18A0072 for j.vieille@controlchaingroup.com; Sun, 22 May 2016 16:05:37 +0200 (CEST) From: diffusion@web2.see.asso.fr Subject: test To: j.vieille@controlchaingroup.com Message-Id: 1463925937.28808@web2.see.asso.fr X-Originating-IP: 80.15.104.74 X-Mailer: Usermin 1.690 Date: Sun, 22 May 2016 16:05:37 +0200 (CEST) MIME-Version: 1.0 Content-Type: multipart/mixed; boundary="bound1463925937" X-Ovh-Tracer-Id: 13596930225495968801 X-Ovh-Remote: 37.187.137.19 (web2.see.asso.fr) X-Ovh-Local: 213.186.33.29 (mx1.ovh.net) X-OVH-SPAMSTATE: OK X-OVH-SPAMSCORE: 0 X-OVH-SPAMCAUSE: gggruggvucftvghtrhhoucdtuddrfeekledrfeekucetufdoteggodetrfdotffvucfrrhhofhhilhgvmecuqfggjfenuceurghilhhouhhtmecufedttdenuc X-Antivirus: avast! (VPS 160522-0, 22/05/2016), Inbound message X-Antivirus-Status: Clean

Is their anyway I can make it work with remote DNS servers? Or do I miss something else?

Thanks for help