Microsoft 365 : Exchange Online / PowerShell – Resolving error – Send-MailMessage : The SMTP server requires a secure connection or the client was not authenticated. The server response was: 5.7.57 Client not authenticated to send mail

Hi All,

Today new issue and solution 🙂

Details / Background

• We have to send an email from one of our PowerShell script
• To send an email we are using Send-MailMessage CMDLET as

PS C:\> Send-MailMessage -from $EmailFrom -To $EmailTo -Subject "Subject - LIFE IS BEAUTIFUL" -Body "LIFE IS BEAUTIFUL" -BodyAsHtml -smtpserver "smtp.office365.com" -usessl -Credential $cred -Port 587

• While executing this “Send-MailMessage” CMDLET we were getting an issue

ISSUE / ERROR

Send-MailMessage : The SMTP server requires a secure connection or the client was not authenticated. The server response was: 5.7.57 Client not authenticated to send mail. Error: 535 5.7.139
Authentication unsuccessful, SmtpClientAuthentication is disabled for the Tenant. Visit https://aka.ms/smtp_auth_disabled for more information. [MA1P287CA0021.INDP287.PROD.OUTLOOK.COM
2023-02-06T14:33:38.610Z 08DB083CF80AB0C7]
At line:1 char:1

• Send-MailMessage -from $EmailFrom -To $EmailTo -Subject “Subject – LI …
• ~~~~~~~~~~~~~~~~~
  • CategoryInfo : InvalidOperation: (System.Net.Mail.SmtpClient:SmtpClient) [Send-MailMessage], SmtpException
  • FullyQualifiedErrorId : SmtpException,Microsoft.PowerShell.Commands.SendMailMessage

Solution

• There is a setting which we need to update from Exchange admin center
• Setting – “Turn off SMTP AUTH protocol for your organization” – this setting is “ON” by default. This means – Microsoft 365 mailboxes have SMTP client authentication disabled by default.
• So we need to enable it.

Steps to enable Microsoft 365 mailboxes SMTP client authentication

• Navigate to Exchange online admin center – either through Microsoft 365 admin center or from direct URL – https://admin.exchange.microsoft.com/
• We have detailed article – How to navigate to Exchange Online admin center – Small Tips and Tricks – Exchange admin center – How to navigate to Exchange admin center
• Once we are in Exchange admin center as

• From left blade click on “Settings” link, we will be redirected to Exchange admin center Settings page as

• From Settings blade click on setting – “Mail flow”
• Right pane will appear – “Mail flow settings” will open as

• As in above figure – “Mail flow settings” – Under “Security” section uncheck the check box for setting – “Turn off SMTP AUTH protocol for your organization” – Save the respective changes
• Once we update the above setting we will be successfully able to send the email as

Thanks for reading !!!

HAVE A FANTASTIC TIME AHEAD !!! LIFE IS BEAUTIFUL 🙂