ok alors après envoi vers mail externe via rainloop:
Sep 7 19:09:33 cloud dovecot: imap-login: Login: user=<michael@xx.net>, method=PLAIN, rip=192.168.x.x, lip=192.168.x.x, mpid=2052, TLS, session=<2gQyUCsflwDAqAIB>
Sep 7 19:09:33 cloud dovecot: imap(michael@xx.net): Disconnected: Logged out in=172 out=1869
Sep 7 19:09:43 cloud dovecot: imap-login: Login: user=<michael@xx.net>, method=PLAIN, rip=192.168.x.x, lip=192.168.x.x, mpid=2057, TLS, session=<8ZLUUCsfmwDAqAIB>
Sep 7 19:09:43 cloud postfix/submission/smtpd[2058]: connect from unknown[192.168.x.x]
Sep 7 19:09:43 cloud postfix/submission/smtpd[2058]: disconnect from unknown[192.168.xx.x]
Sep 7 19:09:43 cloud dovecot: imap(michael@xx.net): Disconnected: Logged out in=11 out=401
Sep 7 19:09:44 cloud dovecot: imap-login: Login: user=<michael@xx.net>, method=PLAIN, rip=192.168.x.x, lip=192.168.x.x, mpid=2061, TLS, session=<+4zaUCsfnQDAqAIB>
Sep 7 19:09:44 cloud dovecot: imap(michael@xx.net): Disconnected: Logged out in=90 out=864
Sep 7 19:10:01 cloud postfix/pickup[1296]: E8CB462F95: uid=0 from=<root>
Sep 7 19:10:02 cloud postfix/cleanup[2067]: E8CB462F95: message-id=<20150907171001.E8CB462F95@cloud.xx.net>
Sep 7 19:10:02 cloud opendkim[648]: E8CB462F95: no signing table match for 'root@cloud.xx.net'
Sep 7 19:10:02 cloud postfix/qmgr[1297]: E8CB462F95: from=<root@cloud.xx.net>, size=668, nrcpt=1 (queue active)
Sep 7 19:10:02 cloud postfix/smtpd[2072]: connect from unknown[192.168.x.x]
Sep 7 19:10:02 cloud postfix/smtp[2071]: warning: host cloud.xx.net[88.121.x.x]:25 greeted me with my own hostname cloud.xx.net
Sep 7 19:10:02 cloud postfix/smtp[2071]: warning: host cloud.xx.net[88.121.x.x]:25 replied to HELO/EHLO with my own hostname cloud.xx.net
Sep 7 19:10:02 cloud postfix/smtp[2071]: E8CB462F95: to=<root@cloud.xx.net>, orig_to=<root>, relay=cloud.xx.net[88.121.x.x]:25, delay=0.2, delays=0.1/0.05/0.05/0, dsn=5.4.6, status=bounced (mail for cloud.xx.net loops back to myself)
Sep 7 19:10:02 cloud postfix/smtpd[2072]: disconnect from unknown[192.168.x.x]
Sep 7 19:10:02 cloud postfix/cleanup[2067]: 1D4C862F9C: message-id=<20150907171002.1D4C862F9C@cloud.xx.net>
Sep 7 19:10:02 cloud postfix/qmgr[1297]: 1D4C862F9C: from=<>, size=2829, nrcpt=1 (queue active)
Sep 7 19:10:02 cloud postfix/bounce[2073]: E8CB462F95: sender non-delivery notification: 1D4C862F9C
Sep 7 19:10:02 cloud postfix/qmgr[1297]: E8CB462F95: removed
Sep 7 19:10:02 cloud postfix/smtpd[2072]: connect from unknown[192.168.x.x]
Sep 7 19:10:02 cloud postfix/smtp[2071]: warning: host cloud.xx.net[88.121.x.x]:25 greeted me with my own hostname cloud.xx.net
Sep 7 19:10:02 cloud postfix/smtp[2071]: warning: host cloud.xx.net[88.121.x.x]:25 replied to HELO/EHLO with my own hostname cloud.xx.net
Sep 7 19:10:02 cloud postfix/smtp[2071]: 1D4C862F9C: to=<root@cloud.xx.net>, relay=cloud.xx.net[88.121.x.x]:25, delay=0.02, delays=0/0/0.02/0, dsn=5.4.6, status=bounced (mail for cloud.xx.net loops back to myself)
Sep 7 19:10:02 cloud postfix/smtpd[2072]: disconnect from unknown[192.168.X.X]
Sep 7 19:10:02 cloud postfix/qmgr[1297]: 1D4C862F9C: removed
Sep 7 19:10:04 cloud dovecot: imap-login: Login: user=<michael@xx.net>, method=PLAIN, rip=192.168.x.x, lip=192.168.x.x, mpid=2074, TLS, session=<VQcOUisfpADAqAIB>
Sep 7 19:10:04 cloud dovecot: imap-login: Login: user=<michael@xx.net>, method=PLAIN, rip=192.168.x.x, lip=192.168.x.x, mpid=2075, TLS, session=<eCIOUisfpQDAqAIB>
Sep 7 19:10:04 cloud dovecot: imap(michael@xx.net): Disconnected: Logged out in=89 out=862
Sep 7 19:10:04 cloud dovecot: imap(michael@xx.net): Disconnected: Logged out in=1961 out=460
J'en ai peut être mis un peut trop mais le test vers une adresse externe m'a donné cela dans le log