I'm not sure how to debug this while my simple mail command used to work, but no longer working right now.
Ex. echo 'test' | mail -s 'test' jdoe@gmail.com
While these commands not working I was able to see these logs
Nov 11 10:20:14 b-world postfix/pickup[2873413]: 12312: uid=0 from=<root@b-world>
Nov 11 10:20:14 b-world postfix/cleanup[2889271]: 12312: message-id=<1.12312@li458-11.members.linode.com>
Nov 11 10:20:14 b-world postfix/qmgr[2846624]: 12312: from=<root@b-world>, size=353, nrcpt=1 (queue active)
Nov 11 10:20:15 b-world postfix/smtp[2889274]: 12312: to=<jdoe@gmail.com>, relay=gmail-smtp-in.l.google.com[2607:f8b0:4002:c09::1a]:25, delay=0.28, delays=0.03/0.01/0.04/0.19, dsn=5.7.1, status=bounced (host gmail-smtp-in.l.google.com[2607:f8b0:4002:c09::1a] said: 550-5.7.1 [2600:3c02::f03c:92ff:febe:4691] Our system has detected that this 550-5.7.1 message does not meet IPv6 sending guidelines regarding PTR records 550-5.7.1 and authentication. Please review 550-5.7.1 https://support.google.com/mail/?p=IPv6AuthError for more information 550 5.7.1 . q188-20020a25d9c5000000b006ccb39d6524si17564ybg.430 - gsmtp (in reply to end of DATA command))
Nov 11 10:20:15 b-world postfix/cleanup[2889271]: 0CAE03F427: message-id=<20221111152015.0CAE03F427@li458-11.members.linode.com>
Nov 11 10:20:15 b-world postfix/bounce[2889293]: 12312: sender non-delivery notification: 0CAE03F427
Nov 11 10:20:15 b-world postfix/qmgr[2846624]: 0CAE03F427: from=<>, size=3175, nrcpt=1 (queue active)
Nov 11 10:20:15 b-world postfix/qmgr[2846624]: 12312: removed
Nov 11 10:20:15 b-world postfix/smtp[2889274]: 0CAE03F427: to=<root@b-world>, relay=none, delay=0.01, delays=0.01/0/0/0, dsn=5.4.6, status=bounced (mail for b-world loops back to myself)
Nov 11 10:20:15 b-world postfix/qmgr[2846624]: 0CAE03F427: removed
And somehow the Fail2ban emails still sending to my inbox fine until now.
So What is going on here ? How can I make my mail command working again from here ?
