I did Inbound SMTP test of https://testconnectivity.microsoft.com/.
Connectivity Test Failed.
Attempting to send a test email message to mine@keyman .com using MX <mymail.domain.com>
Delivery of the test email message failed.
Additional Details
The server returned status code 530 - The SMTP server requires a secure connection or the client was not authenticated. The server response was: 5.7.1 Client was not authenticated
Exception details:
Message: The SMTP server requires a secure connection or the client was not authenticated. The server response was: 5.7.1 Client was not authenticated
Type: System.Net.Mail.SmtpException
Stack trace:
at System.Net.Mail.MailCommand.CheckResponse(SmtpStatusCode statusCode, String response)
at System.Net.Mail.MailCommand.Send(SmtpConnection conn, Byte[] command, MailAddress from, Boolean allowUnicode)
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 Microsoft.M365.RCA.ConnectivityTests.SmtpMessageTest.PerformSmtpMessageTest(RcaTestContext parent, String mailExchangerHost, ISmtpAddress emailAddress, ContextInfo contextInfo, SmtpOptions smtpOptions)