When you test and enable a mailbox in Dynamics 365 (formerly known as Dynamics CRM Online), you encounter one of the following errors in the Alerts area:
- The email message "Test Message" cannot be sent because an error occurred while establishing a secure connection to the email server. Mailbox <Mailbox Name> didn't synchronize. The owner of the email server profile <Email Server Profile Name> has been notified.
Email Server Error Code: Smtp server returned 530 MustIssueStartTlsFirst exception.
ActivityId: <GUID>
>Error : System.Net.Mail.SmtpException: The SMTP server requires a secure connection or the client was not authenticated. The server response was: 5.5.1 Authentication Required. Learn more at
at System.Net.Mail.SendMailAsyncResult.End(IAsyncResult result)
at System.Net.Mail.SmtpTransport.EndSendMail(IAsyncResult result)
at System.Net.Mail.SmtpClient.SendMailCallback(IAsyncResult result) - Email cannot be received for the mailbox <Mailbox Name>. Make sure that the credentials specified in the mailbox are correct and have sufficient permissions for receiving email. Then, enable the mailbox for email processing.
- Email cannot be received for the mailbox <Mailbox Name>. Make sure that the credentials specified in the mailbox are correct and have sufficient permissions for receiving email. Then, enable the mailbox for email processing.