Email undeliverable when Email Account Configured with Exchange's SMTP ServerIssue Email undeliverable when Email Account Configured with Exchange's SMTP Server Symptoms -Using server smtp.office365.com -port 587 is configured -Error in node logs show: com.sun.mail.smtp.SMTPSendFailedException: 530 5.7.57 SMTP; Client was not authenticated to send anonymous mail during MAIL FROMCauseWhen connecting to the Exchange endpoint smtp.office365.com, it is required to authenticate with a user that has an Exchange Online mailbox and that the SMTP sender email account is configured to use TLS. ResolutionEnabling TLS for your SMTP email account Navigate to email account Select Connection Security with TLS Related LinksPlease see Non-delivery reports in Exchange Online (https://docs.microsoft.com/en-us/exchange/mail-flow-best-practices/non-delivery-reports-in-exchange-online/non-delivery-reports-in-exchange-online).