The relevant log ines is:
Mar 14 13:09:03 mail postfix/smtp[1518]: A881B435EE: to=<ayman.makram@mcvcomercial.cu>, relay=172.16.5.233[172.16.5.233]:25, delay=0.3, delays=0.05/0.03/0.07/0.15, dsn=5.0.0, status=bounced (host 172.16.5.233[172.16.5.233] said: 554 Message is not RFC compliant (in...