Very strange issue shared mailbox.
It was working previously without any issues.
The below is setting which had been working for the past few months.
We are able to sent out emails from this shared mailbox successfully.
This setting is as indicated in the link as below.
We added the user to the Full Access as well as Send as.
The below is the error we are getting these few weeks - we are not able to send mails out from this shared mailbox currently.
Is this a bug or I made some mistake in the settings?