You left out pretty much all the information, actually. How did you configure Evolution? What are your POP settings? Something must be setup wrong in the server configuration, probably the server address or port.
Also, you should get in the habit of creating more descriptive topic titles, as that will tend to get you help faster. For example "Ubuntu email" doesn't really describe this issue in the least, as the problem is with the configuration of Evolution and has nothing to do with Ubuntu.