When the Exchange Receive Connector is configured just for using "Integrated Windows Authentication", we can receive the following error:
The server response was: 5.7.1 Client was not authenticated
Email NOT sent with the following error(s): SMTP host: xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx'; SSL: 'False' - SaaS.WebUI.Action.SendEmailActionDefException: SendAsyncEmail [TenantId=IMTServiceCentre, UserId=xxxxxxxxxxxx]. ---> System.Net.Mail.SmtpException: The SMTP server requires a secure connection or the client was not authenticated. The server response was: 5.7.1 Client was not authenticated at System.Net.Mail.MailCommand.CheckResponse(SmtpStatusCode statusCode, String response) at System.Net.Mail.SmtpTransport.SendMail(MailAddress sender, MailAddressCollection recipients, String deliveryNotify, Boolean allowUnicode, SmtpFailedRecipientException& exception) at System.Net.Mail.SmtpClient.Send(MailMessage message) at SaaS.WebUI.Action.SendEmailActionDef.SendAsyncEmail(Object p) --- End of inner exception stack trace ---.
At the moment this article has been written related to version 2015.1.2. it is not possible to use the Windows credentials for sending an email, so it is necessary to configure the Hub Transport for allowing at least Basic Authentication for SMTP.