The StruxureOn Gateway gathers the event.txt log daily for most APC devices using the Gateway's FTP credentials, apc/apc by default. If the Gateway credentials do not match those on the device, a warning email message is sent every day for each device: Warning: System detected an unauthorized user attempting to access the FTP interface from <IP address>.
Change the FTP settings in the More > Device File Transfer Settings option in the Gateway to match those on the device.