unable to send email

Question

Hi All

I am trying to trigger a test email using the below syntax i am getting error. if i am using onprem relay i am not seeing any issue if i use office365 relay i am facing issue. exchange online plan1 license is assigned to the service account. sender and recipient email is my domain.

Send-MailMessage -SmtpServer smtp.office365.com -Credential $credential -From 'svcacct@contoso.com' -To 'user1@contoso.com' -Subject 'Test' -Port 587 -UseSsl STARTTLS

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, the user credentials were incorrect.

Answer 1

Hi Glenn Maxwell,

Please use the following command:

Send-MailMessage -SmtpServer smtp.office365.com -Credential $credential -From 'svcacct@contoso.com' -To 'user1@contoso.com' -Subject 'Test' -Port 587 -UseSsl

 

Note: that the -UseTSSL switch should not use any parameters, such as STARTTLS.

 

In addition, check the following settings for SMTP AUTH:

1. Disabling security defaults
2. Check if SMTP authentication is enabled for this user
3. Exclude the user from a Conditional Access policy that blocks Legacy Authentication
4. Disable Multi-Factor Authentication (MFA) on the licensed mailbox that's being used

Please refer to this link for details： Fix issues with printers, scanners, and LOB apps that send email using Microsoft 365 - Exchange | Microsoft Learn

---

If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".

Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.

Answer 2

I am getting the below error when i remove ssl

Send-MailMessage -SmtpServer smtp.office365.com -Credential $credential -From  'svcacct@contoso.com' -To ' user1@contoso.com ' -Subject 'Test' -Port 587 STARTTLS

The server response was: 5.7.3 STARTTLS is required to send mail