Engloid

Can you just set it so that the areas the cat walks (close to the floor) won't pick up motion and send emails?

Yeah, it may be just poor cameras. Have you tried adding infrared light to the area to see if that helps? To test, you can get another camera and just run the power cable to it. When it's dark, the LED's will turn on and add more light. If that works well enough for you, they sell some add on infrafed led's on ebay.

I have a swann 4500. I want to make it store video to a Synology NAS. I also would like to limit the amount of stuff it stores, so it doesn't just fill up my NAS.

I have the Swannview Plus software on the computer and can also access the dvr through a monitor that's attached.

Any help on how to do this is appreciated.