postmaster:     root
bounces: root

transport_maps = hash:/etc/postfix/transport

bounces@example   bulkbounce:

bulkbounce   unix  -       n       n       -       -       pipe
  user=nobody argv=/etc/postfix/bounce_hold.php ${recipient}

Mar  6 15:00:11 smtp160218 syslog/smtp[404]: 8BF363D6: to=<test@testing.com>, relay=mail.fabulous.com[104.171.24.195]:25, delay=1.4, delays=0.57/0.02/0.68/0.16, dsn=5.1.1, status=bounced (host mail.fabulous.com[104.171.24.195] said: 550 5.1.1 <test@testing.com>: Recipient address rejected: User unknown in virtual alias table (in reply to RCPT TO command))
Mar  6 15:00:11 smtp160218 postfix/cleanup[403]: F38473E0: message-id=<20180306150011.F38473E0@smtp160218.smtpmailgob.com>
Mar  6 15:00:11 smtp160218 postfix/qmgr[384]: F38473E0: from=<>, size=5856, nrcpt=1 (queue active)
Mar  6 15:00:12 smtp160218 postfix/bounce[405]: 8BF363D6: sender non-delivery notification: F38473E0
Mar  6 15:00:12 smtp160218 postfix/qmgr[384]: 8BF363D6: removed
Mar  6 15:00:12 smtp160218 postfix/pipe[406]: F38473E0: to=<bounces@example.com>, relay=bulkbounce, delay=0.05, delays=0/0.01/0/0.03, dsn=2.0.0, status=sent (delivered via bulkbounce service)

syslog/smtp[3048]: 947433D6: to=<test@testing.com>, relay=mail.fabulous.com[104.171.24.195]:25, delay=1.8, delays=0.65/0.01/0.98/0.16, dsn=5.1.1, status=bounced (host mail.fabulous.com[104.171.24.195] said: 550 5.1.1 <test@testing.com>: Recipient address rejected: User unknown in virtual alias table (in reply to RCPT TO command))
Mar  6 17:22:26 smtp160218 postfix/cleanup[3047]: 5E0113E0: message-id=<20180306172226.5E0113E0@smtp160218.example.com>
Mar  6 17:22:26 smtp160218 postfix/bounce[3050]: 947433D6: sender non-delivery notification: 5E0113E0
Mar  6 17:22:26 smtp160218 postfix/qmgr[3032]: 5E0113E0: from=<>, size=5913, nrcpt=1 (queue active)
Mar  6 17:22:26 smtp160218 postfix/randomizer[3046]: Using: smtp2: Transport Service
Mar  6 17:22:26 smtp160218 postfix/qmgr[3032]: 947433D6: removed
Mar  6 17:22:26 smtp160218 syslog/smtp[3051]: 5E0113E0: to=<bounces+sadasdasdasdasdasd@example.com>, relay=none, delay=0.09, delays=0/0.01/0.07/0, dsn=5.4.6, status=bounced (mail for example.com loops back to myself)
Mar  6 17:22:26 smtp160218 postfix/qmgr[3032]: 5E0113E0: removed