$ grep  AE928360291 /var/log/mail.log
May 29 08:36:26 $MSERVER postfix/submission/smtpd[32273]: AE928360291: client=XXXXXXX.XXX.XXXXX-XXX.XX.XX[XXX.XXX.XXX.XXX], sasl_method=CRAM-MD5, sasl_username=$USER
May 29 08:36:26 $MSERVER postfix/cleanup[32278]: AE928360291: message-id=<20180529083626.ef2d3ee7bf4e6c0c581b41dd@kuzuore.com>
May 29 08:36:26 $MSERVER postfix/qmgr[12418]: AE928360291: from=<$USER@kuzuore.com>, size=614, nrcpt=2 (queue active)
May 29 08:36:29 $MSERVER postfix/smtp[32280]: AE928360291: host gmail-smtp-in.l.google.com[2404:6800:4008:c03::1a] said: 421-4.7.0 [2401:2500:102:3030:153:126:188:64      15] Our system has detected an 421-4.7.0 unusual rate of unsolicited mail originating from your IP address. To 421-4.7.0 protect our users from spam, mail sent from your IP address has been 421-4.7.0 temporarily rate limited. Please visit 421-4.7.0  https://support.google.com/mail/?p=UnsolicitedRateLimitError to 421 4.7.0 review our Bulk Email Senders Guidelines. 9-v6si3001033ple.104 - gsmtp (in reply to end of DATA command)
May 29 08:36:30 $MSERVER postfix/smtp[32280]: AE928360291: to=<$AUSER@gmail.com>, relay=gmail-smtp-in.l.google.com[74.125.203.26]:25, delay=4.3, delays=0.28/0.05/3.6/0.39, dsn=2.0.0, status=sent (250 2.0.0 OK 1527550590 f64-v6si31397818plf.496 - gsmtp)
May 29 08:36:31 $MSERVER postfix/smtp[32279]: AE928360291: to=<$BUSER@DOMAIN>, relay=YYYYYYYYYY.YYY[YYY.YYY.YYY.YYY] :25, delay=5.2, delays=0.28/0.03/0.96/3.9, dsn=2.0.0, status=sent (250 2.0.0 Ok: queued as 460D11D1)
May 29 08:36:31 $MSERVER postfix/qmgr[12418]: AE928360291: removed