Hi Prasadd,
1) First the email syntax validation.
I have written an article on this at the following link. In short, you can use regular expressions:
Email Validation
2) Send email from a desktop application.
You can use the SmtpMail class just as you would in an ASP.NET application. You just need to add a reference to the System.Web.dll library. If you are using Visual Studio .NET, go to the Solution Explorer and right click 'References' in your project. Choose to Add Reference. Then browse the .NET tab for System.Web.dll and add it. Then the following should work.
System.Web.Mail.SmtpMail.SmtpServer = "your server";
string to = "you@email.com";
string from = "someone@email.com";
string subject = "Email Test";
string body = "Test Body";
Sysetm.Web.Mail.SmtpMail.SmtpServer.Send(to, from subject, body);
Cheers,
Steve