Email messages not being sent out for our Service Requests. This works for Incidents, Error in the Email logs shows:
System.Net.Mail.SmtpException: Mailbox unavailable. The Server response was: 5.7.1 Client does not have permissions to send as this sender as System.Net.Mail.MailCommand.....
It was determined that the Incidents email was being sent from the Incidents@domain.com address (example) but the Service Requests email was being sent from the ServiceRequests@domain.com address.
The account that is configured to send outgoing emails in the Email Configuration is configured as Incidents@domain.com. This account should have "send as" rights to the ServiceRequests@domain.com account in Exchange/AD.
**Note: Granting "full" rights did not resolve the issue, it needed to have the specific "send as" right enabled.
Once this was configured the emails from both the Incidents@domain.com and ServiceRequests@domain.com addresses could be sent.