Does this method look to Web.CurrentUser properties to derive a ‘from’ address or will it use some sort of SharePoint default system e-mail address? I can’t see anything mentioned in the documentation:
http://msdn.microsoft.com/en-us/library/ms477270.aspx
I know how to explicitly set it by ‘manually’ retrieving this info myself and adding headers – but I don’t know if it’s just unnecessary.
Do you have access to central admin?
If you do i believe that the email it will send from would be the one thats set in central admin under system settings -> E-mail and text messaging -> Outgoing EMails Settings.
Don’t hold me to this but it may be wrong