Yep,
J'ai retesté justement comme il le faut, et même soucis.
root@vps-19004:~# tail -f /var/log/mail.log
Oct 23 18:05:52 vps-19004 postfix/local[15416]: 77D2F3960080: to=<cyprien??XXX@vps-XXX>, orig_to=<root@vps-19004.XXX>, relay=local, delay=0.08, delays=0.05/0/0/0.03, dsn=5.1.1, status=bounced (unknown user: "cyprien??dystopie.faith")
Oct 23 18:05:52 vps-19004 postfix/cleanup[15407]: 871DC3960083: message-id=<20161023220552.871DC3960083@vps-XXXX>
Oct 23 18:05:52 vps-19004 postfix/qmgr[15384]: 871DC3960083: from=<>, size=2327, nrcpt=1 (queue active)
Oct 23 18:05:52 vps-19004 postfix/bounce[15417]: 77D2F3960080: sender non-delivery notification: 871DC3960083
Oct 23 18:05:52 vps-19004 postfix/qmgr[15384]: 77D2F3960080: removed
Oct 23 18:05:52 vps-19004 postfix/local[15416]: 871DC3960083: to=<cyprien??XXX@vps-19004.XXX>, orig_to=<root@vps-XXXX>, relay=local, delay=0.07, delays=0.03/0/0/0.04, dsn=5.1.1, status=bounced (unknown user: "cyprien??XXX")
Oct 23 18:05:52 vps-19004 postfix/qmgr[15384]: 871DC3960083: removed
Oct 23 18:06:16 vps-19004 postfix/smtp[15409]: connect to mx00.gmx.net[212.227.15.10]:25: Connection timed out
Oct 23 18:06:46 vps-19004 postfix/smtp[15409]: connect to mx01.gmx.net[212.227.17.4]:25: Connection timed out
Oct 23 18:06:46 vps-19004 postfix/smtp[15409]: 29E5D396007E: to=<cyprien.XXXX@XXXX.fr>, relay=none, delay=60, delays=0.05/0/60/0, dsn=4.4.1, status=deferred (connect to mx01.gmx.net[212.227.17.4]:25: Connection timed out)