Issue while configuring SMTP using O365

Suganthan Kumar (AP) 1 Reputation point
2021-10-07T09:36:54.19+00:00

Hi,

I cant able to send mails using SMTP via O365.I have enabled the SMTP AUTH in mail apps.While i try to send mails through SMTP got the below 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 5.7.3 Authentication unsuccessful [SG2PR03CA0140.apcprd03.prod.outlook.com]"

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  1. Andy David - MVP 141.5K Reputation points MVP
    2021-10-07T11:44:39.29+00:00

    Is the account MFA enabled?

    1 person found this answer helpful.
    0 comments
  2. Kael Yao-MSFT 37,496 Reputation points Microsoft Vendor
    2021-10-08T01:16:16.003+00:00

    Hi @Suganthan Kumar (AP)

    Please refer to this link for troubleshooting: Fix issues with printers, scanners, and LOB applications that send email using Microsoft 365 or Office 365

    There are four possible causes of this issue:

    1. SMTP AUTH is not enabled on the mailbox being used
    2. MFA is enabled on the mailbox
    3. Azure Security Defaults is enabled in the tenant
    4. The user is included in a Conditional Access policy which blocks Legacy Authentication

    If the response is helpful, please click "Accept Answer" and upvote it.
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