Client's email reputation per all major RBL is clear yet this issue persists. Please advise @symantec crew. Error message follows:
This is the mail delivery agent at Symantec Email Security.cloud.
I was unable to deliver your message to the following addresses:
oonclaims@eyewearspecialoffers.com
Reason: 530 5.7.57 Client not authenticated to send mail. [MWHPR04CA0043.namprd04.prod.outlook.com]
The message subject was: FW: Claim Form Submission The message date was: Tue, 21 Sep 2021 12:20:53 +0000 The message identifier was: BB/DB-16221-B2EC9416 The message reference was: server-4.tower-402.messagelabs.com!1632226856!71940!1
Please do not reply to this email as it is sent from an unattended mailbox.
Contact your email administrator if you need more information, or instructions for resolving this issue.