Client authentification failure while sending email from office365 account via powershell

[remberme]

Hi I'm trying to send email from office365 account in powershell, but got client not authenticated failure:

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.

I have tried powershell native "Send-MailMessage" and MailKit and got same errors. Really need your help to figure out the problem. Thanks!

[#2]

Can you provide the exact PowerShell command you’re using including the parameters you’re setting? Of course edit any potential sensitive info.

[#3]

@pvanberlo, I'm trying commands below. Now I can use it or MailKit to send email after turning off the Authenticator approval. How can I achieve it when authenticator is turning on?

$cred = Get-Credential
$mail = @{
SmtpServer = 'smtp.office365.com'
Port='587'
UseSSL=$true
From='user@domain'
To='targetuser@emailserver'
Subject='subject'
Body='body'
}
Send-MailMessage @mail # or Use MailKit, see https://adamtheautomator.com/powershell-email/

[#4 · Accepted solution]

The regular way to do this when using modern authentication with MFA would be to allow ‘app passwords’. There are other ways, which I would not recommend, because they potentially lower the security posture.

https://docs.microsoft.com/en-us/azure/active-directory/user-help/multi-factor-authentication-end-us...

If that doesn't work or is not allowed in your tenant, other methods may include:

* Disabling MFA (not recommended)

* If MFA is enabled using Azure AD Conditional Access, exclude this user for specifically SMTP from the Azure AD Conditional Access policy

* If you're using Security Defaults within your Microsoft 365 tenant, legacy authentication is blocked by default and can't be bypassed unless you disable Security Defaults

* You can use the Graph API for sending out e-mail programatically (Send mail - Microsoft Graph v1.0 | Microsoft Docs)

[#5]

@remberme 

I tested using outlook of my personal email. Try to fill with 365 SMTP:

$cred = Get-Credential
$SMTPServer = "smtp-mail.outlook.com"
$Port = "587"
$From = "user@domain"
$To = "targetuser@emailserver”
$Subject = "subject"
$Body = "Body"
Send-MailMessage -From $From -to $To -Subject $Subject -Body $Body -BodyAsHtml -SmtpServer $SMTPServer -Port $Port -UseSsl -Credential $cred 

[#6]

I have the same problem, I'm trying to respond to my Outlook emails but it return back to me. Please help

[#7]

@Laila_Taik
How about emailing using outlook directly without the need of smtp.

https://techcommunity.microsoft.com/t5/windows-powershell/using-outlook-application-to-email/m-p/344...

[#8]

Thank you, I 'll Try.