ProSites Email Headers | How to Change Headers (from email)

I am using Mandrill to take on our email load, and it looks like ProSites is using the user's admin email addresses to send email noticed, specifically the Expiration notice. This creates an email which is not signed and will not be sent to the user to alert them.

How can I alter this code in ProSites to use an arbitrary email instead of the administrative user's email?