If you use a regular IP camera or DVR/NVR, then the image or video resolution must be set from your device. CameraFTP cloud system will not resize your images/videos.
In your case, please log on to your camera's configuration page (not on CameraFTP website) and set the image resolution or video profile. Some cameras can set multiple video profiles. In this case, please make sure to select a correct video profile for uploading to FTP or SMTP server.