SmtpClient Class allows applications to send e-mail by using the Simple Mail Transfer Protocol (SMTP). Instead of assigning properties of this class in C# , we can use the <system.net> element in the web.config as shown below :

<system.net>
    <mailSettings>
        <smtp from = "email@abc.com">
            <network 
                host = "mail.abc.com"
                port = "25"
                password = "password"
                userName = "email@abc.com"
                defaultCredentials = "false"
                enableSsl = "true"
             />
         </smtp>
     </mailSettings>
 </system.net>

The advantage of this approach is that we can change the mail settings without having to rebuild the entire application.

Hope this helps :)

Further Reading :
Sending Email with System.Net.Mail