azure app service office 365 exception The SMTP server requires a secure connection or the client was not authenticated

Question

Exception while sending email smtp.office365.com

It works perfectly fine when I run the application on my desktop but I am getting the error when I run the application hosted in azure app service. 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 request did not meet the criteria to be authenticated successfully. Contact your administrator. [MN2PR01CA0012.prod.exchangelabs.com 2024-03-18T11:50:52.999Z 08DC46A303522B72]

"EmailSettings": {

"Host": "smtp.office365.com",

"Port": 587,

"EnableSsl": true,

"Username": "****",

"Password": "****",

"FromAddress": "**"

},

Answer 1

@Murugan Andezuthu Dharmaratnam Thanks for reply!

SMTP authentication does not work well in an environment were MFA is enabled , this could be happening because of that.

You may refer to the article How to set up a multifunction device or application to send email using Microsoft 365 or Office 365 | Microsoft Docs to view the requirements and limitations of smtp.

Kindly try the following:

1. In the Azure portal, on the left navigation bar, click Microsoft Entra ID
2. On the Overview page, in feature highlights section, click Conditional Access.
3. Go to  Microsoft Azure , sign in with a global admin account
4. On the Conditional Access page, check the policies and modify them.

Let us know