When we encounter an error "BDAT command has been rejected by the server. The server responded: 550 5.7.1 Client does not have permissions to send as this sender.", during SMTP configuration, the following needs to be updated.
Go to Settings > Monitoring and Notification > Format Email Template
Change the from email address which by default is email@example.com, change it to your own email address and do the same on the SMTP Admin email.