Okay, created a new Mail Host with only 'list.example.com' and no alias domain. I then created a new list and tried subscribe/unsubscribe but got the following error message in mail.log file
Dec 17 21:14:26 mailman3 postfix/smtpd[6649]: 057E744552: client=localhost[127.0.0.1] Dec 17 21:14:26 mailman3 postfix/cleanup[6653]: 057E744552: message-id=<170284766462.1144.7361224077829393518@ec2-54-172-107-21.compute-1.amazonaws.com> Dec 17 21:14:26 mailman3 postfix/qmgr[6644]: 057E744552: from=<list_test-bounces@lists.example.com>, size=908, nrcpt=1 (queue active) Dec 17 21:14:26 mailman3 postfix/smtpd[6649]: disconnect from localhost[127.0.0.1] ehlo=1 mail=1 rcpt=1 data=1 quit=1 commands=5 Dec 17 21:14:27 mailman3 postfix/smtp[6654]: 057E744552: to=<eboltz@lhtservices.com>, relay=mail.smtp2go.com[45.79.114.202]:587, delay=1, delays=0.01/0.01/0.52/0.46, dsn=5.0.0, status=bounced (host mail.smtp2go.com[45.79.114.202] said: 550-From header sender domain not verified (lists.example.com) 550-On your Sending > Verified Senders page 550 verify the sender domain or email to be allowed to send. (in reply to end of DATA command)) Dec 17 21:14:27 mailman3 postfix/cleanup[6653]: 054DD4455A: message-id=<20231217211427.054DD4455A@lists.example.com> Dec 17 21:14:27 mailman3 postfix/bounce[6655]: 057E744552: sender non-delivery notification: 054DD4455A Dec 17 21:14:27 mailman3 postfix/qmgr[6644]: 054DD4455A: from=<>, size=3253, nrcpt=1 (queue active) Dec 17 21:14:27 mailman3 postfix/qmgr[6644]: 057E744552: removed Dec 17 21:14:27 mailman3 postfix/local[6656]: 054DD4455A: to=<list_test-bounces@lists.example.com>, relay=local, delay=0.01, delays=0/0/0/0, dsn=5.1.1, status=bounced (unknown user: "list_test-bounces") Dec 17 21:14:27 mailman3 postfix/qmgr[6644]: 054DD4455A: removed Dec 17 21:14:43 mailman3 postfix/smtpd[6649]: connect from localhost[127.0.0.1] Dec 17 21:14:43 mailman3 postfix/smtpd[6649]: 1030044552: client=localhost[127.0.0.1] Dec 17 21:14:43 mailman3 postfix/cleanup[6653]: 1030044552: message-id=<170284768167.1143.3082499628069977260@ec2-54-172-107-21.compute-1.amazonaws.com> Dec 17 21:14:43 mailman3 postfix/qmgr[6644]: 1030044552: from=<list_test-bounces@lists.example.com>, size=1505, nrcpt=1 (queue active) Dec 17 21:14:43 mailman3 postfix/smtpd[6649]: disconnect from localhost[127.0.0.1] ehlo=1 mail=1 rcpt=1 data=1 quit=1 commands=5 Dec 17 21:14:43 mailman3 postfix/smtp[6654]: 1030044552: to=<eboltz@lhtservices.com>, relay=mail.smtp2go.com[66.228.43.14]:587, delay=0.36, delays=0/0/0.12/0.23, dsn=5.0.0, status=bounced (host mail.smtp2go.com[66.228.43.14] said: 550-From header sender domain not verified (lists.example.com) 550-On your Sending > Verified Senders page 550 verify the sender domain or email to be allowed to send. (in reply to end of DATA command)) Dec 17 21:14:43 mailman3 postfix/cleanup[6653]: 6881D4455A: message-id=<20231217211443.6881D4455A@lists.example.com> Dec 17 21:14:43 mailman3 postfix/bounce[6655]: 1030044552: sender non-delivery notification: 6881D4455A Dec 17 21:14:43 mailman3 postfix/qmgr[6644]: 6881D4455A: from=<>, size=3849, nrcpt=1 (queue active) Dec 17 21:14:43 mailman3 postfix/qmgr[6644]: 1030044552: removed Dec 17 21:14:43 mailman3 postfix/local[6656]: 6881D4455A: to=<list_test-bounces@lists.example.com>, relay=local, delay=0.01, delays=0/0/0/0, dsn=5.1.1, status=bounced (unknown user: "list_test-bounces") Dec 17 21:14:43 mailman3 postfix/qmgr[6644]: 6881D4455A: removed
I'll check my SPF records, see if there is something amiss with them as well