Multiple number of notifications are being sent to server administrator and to reseller. It happens when one of reseller's customer exceeds his resources. Reseller has enough resources.
Example of received notification:
The 'John_Reseller' account is approaching or already exceeded the limits:
This issue has been considered as software issue #PPPM-1489.
The issue was fixed in microupdate #7 for Plesk 12.0.18 MU#7. To fix the issue make sure latest MU are installed:
# /usr/local/psa/admin/sbin/autoinstaller --select-product-id ppsmbe --select-release-current --reinstall-patch --install-component base
%plesk_dir%\admin\bin\ai.exe --select-product-id panel --select-release-current --reinstall-patch --install-component base