Email responses to be sent for the Customers from assigned workflows are failing - manual notification emails are sent successfully. Upon checking "Admin > Logs > Outbound email logs" we see that the send is failing and the "Email History" tab has the below error:
Failed Mailbox unavailable. The server response was: 5.7.60 SMTP; Client does not have permissions to send as this sender [xxxx.prod.outlook.com]
The email address used in the email template of the workflows does not have permissions to send on behalf. This error is seen when Office 365 works with unknown emails.
Follow these steps:
1. Check the email template associated with the workflow.
2. Edit the email address in the email template of the workflow. Make sure the sender mail address matches the domain handled by your SMTP server:
3. Save the changes and check if the emails are now sent successfully.
Applies to: O365 Mail Servers used in BMS.