For my newly installed site using Paradise template, within Acymailing component, the super user's email is "ivovalkov@abv.bg", in spite of the same user's email being something else.
When I try to edit this in the component, I get to a new Joomla user creation screen with a warning message saying :
"JUser: :_load: Unable to load user with ID: 667"
I think this could be a bug from your end instead of Acymailing's.