How come the email sent from a smart action shows it's sent from [e-mail]?

To send email on behalf of the user, you must integrate Oracle Sales in the Redwood User Experience with Microsoft Exchange 365. When you complete the integration, the sent email shows up in both the user's sent items folder and is captured in Oracle Sales as well.

To learn how to set up the integration, see the How do I implement Microsoft 365 for Oracle Sales Redwood UX? guide.