I was trying to send Emails using SSIS package deployed in SQL 2008. I was getting this error when i am trying to run the SQL Agent Job which sends Email address on the success of this job.
Error message in event log:
"Mailbox unavailable. The server response was: 5.7.1 Client does not have permissions to send as this sender".
To fix this problem check the following:
1) Check the service account for SQL Agent Service in your server.
2) Make sure the service account is a domain account, because if the system administrator doesn't allow to send emails for anonymous users, then this is one of the main reasons to get this error.
3) Don't forget to restart the SQL service agent if you changed the service account.
4) Inform your system administrator to add anonymous users with a new receive connector in Exchange, check this article:
5) Make sure in your SSIS Package you check use windows authentication checkbox in the SMTP Connection manager.
Hope this helps.