Fix: Send-MailMessage : The SMTP server requires a secure connection or the client was not authenticated

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Problem

You might have received the below error message when you try to send mail using the Send-MailMessage cmdlet.

Send-MailMessage : The SMTP server requires a secure connection or the client was not authenticated. The server
response was: 5.7.57 SMTP; Client was not authenticated to send anonymous mail during MAIL FROM
[PSXP216CAXXXX.XXXXXX.PROD.OUTLOOK.COM]
At line:1 char:1
+ Send-MailMessage -To "[email protected]" -from "admin ...
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidOperation: (System.Net.Mail.SmtpClient:SmtpClient) [Send-MailMessage], SmtpExcept
   ion
    + FullyQualifiedErrorId : SmtpException,Microsoft.PowerShell.Commands.SendMailMessage

I have used the below script to send mail using Office 365 user account. In my case, I have got the above error while providing wrong password in my script and the problem solved after providing correct user credentials.

$username = "[email protected]"
$password = "user_password"
$sstr = ConvertTo-SecureString -string $password -AsPlainText -Force
$cred = New-Object System.Management.Automation.PSCredential -argumentlist $username, $sstr
$body = "This is a test email"
Send-MailMessage -To "[email protected]" -From "[email protected]" -Subject 'Test message' -Body $body -BodyAsHtml -SmtpServer smtp.office365.com -UseSSL -Credential $cred -Port 587

Cause/Solution

  • Possible Reason 1: Ensure that you have provided the correct user credentials (User name and password).
  • Possible Reason 2: For Microsoft Office 365 account, ensure the Authenticated client SMTP submission enabled in Exchange Online. Read this post for more details.
  • Possible Reason 3: Ensure that you have provided the same user account for both the Credential and From fields.
  • Possible Reason 4: If you want to send mail on behalf of another user, then ensure that the user account has required permissions (ex: SendAs or SendOnBehalf) for the account that you provided in From field.
  • Possible Reason 5: If you face the issue with MFA enabled account, then you can generate an app password and then use an app password for that account, instead of the regular user password. Related thread: https://techcommunity.microsoft.com/t5/Identity-Authentication/Send-Mail-SMTP-through-Office-365-with-MFA/m-p/163867
  • Possible Reason 6: Make sure that you have used the option –UseSSL if your SMTP server requires a secure connection.

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