I did some other checks and I talked with developers. They told me that there is an error. Because, currently, if you don't set any email address in any level of "Currency and Payments System" the email address set under HSNM System Settings (Administrator Email Address) is used to send payments notifications.
Starting from next HSNM version, available soon, only the email address set under "Currency and Payments System" will be considered.
Hope to help you,