Webmail lite ASP.NET issue?

Hi,
I have downloaded webmail lite asp.net website and try to build, I am getting below error-
The type 'Domain' exists in both '10_App_Code, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null' and 'WebMail, Version=5.1.3.0, Culture=neutral, PublicKeyToken=null'
If anyone already worked on this issue then let me know.

Thanks.