You need to be able to assign a specific SENDER email address within a workflow
Mike Will commented
If this cannot be done, adding the ability to have the Replyto set on the email could work as well.
Joao Penha-Lopes commented
Give Kevin a large beer and put it on my tab. a) Joao
Please provide the option to send email from a different address in the workflow, not all departments within an organisation want the emails to come from the same address.