problem on sensing Email using smtp, c# - urgent,pls help

Hi,

I am a newby in c#. I want to send an email using smtp. I got the error "type or namespace name smtp could not be found". I wanted then to add the line: using System.Web.Mail but thisnamespace is not recognized (the part with .Mail is not known). Should I add some reference or what should I do in order for my tool to be able to send an email?

Thank you very much!
Serban