Hi Prathap,
This is due to Configurations from your admin side.
You can ask your admin to do Authenticated SMTP changes as mentioned below on the configuration end.
Changes to do : –
Open the Microsoft 365 admin center and go to Users > Active users.
Select the user, and in the flyout that appears, click Mail.
In the Email apps section, click Manage email apps.
Verify the Authenticated SMTP setting: unchecked = disabled, checked = enabled.
When you're finished, click Save changes.
Hope this will help you.!
Cheers.