It looks like you are using the "Send an email notification" action to send the email. It is generally accepted that use of this action is discouraged. You cannot control the sender when using this connection and emails sent usually end up in junk email.
My suggestion is to create a shared mailbox and make sure that you have permissions to send from the shared mailbox. Remove the Send an email notification action. Then, use the Send an email from a shared mailbox action. The sender will be the shared mailbox, so name the mailbox appropriately.
Another alternative is just to substitute the Office 365 Outlook Send an email action. The downside is that it will show as being sent from you or the connection that you use with the action.
