Appointments+ 'From Email' on Multisite

We are using the Appointments+ plugin on a multisite installation.... working great!

This isn't the issue though. Our problem is with the 'From Email' when a customer is emailed the notification. Emails are sent to the service provider, customer and admin as expected. The 'From Email' is neither the admin email now the service providers email. See the screenshot to see the from email. In my gmail account, it says it from ' via'. Oddly enough, we do not have mandrill installed on this site. We do have mandrill installed on the main network site though, but why would this affect our sub-domain site?

Is there a way to set a custom reply to or from email in the settings?