The mail settings you entered were not valid. Error thrown was: javax.mail.AuthenticationFailedException: 535 5.7.3 Authentication unsuccessful [DB7PR02CA0016.eurprd02.prod.outlook.com]
What could be a cause of the error? I know that user credentials are correct.
By the initial look of the error and since you have the right credentials, I suspect the issue maybe with the MS Exchange mail server. Probably the user account is not allowed to send an email via a relay. Kindly confirm this with the MS administrator of the Exchange server.
Also check if the SMTP port is opened on firewall.