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 <> element in the web.config as shown below :

        <smtp from = "">
                host = ""
                port = "25"
                password = "password"
                userName = ""
                defaultCredentials = "false"
                enableSsl = "true"

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