Instead using the ASP.Net email sending code, we can use the following code to send email in Umbraco web applications.

Web.Config Configuration:

Gmail SMTP Settings:

<system.net>
    <mailSettings>
      <smtp>
        <network
         host="smtp.gmail.com"
         port="587"
         userName="email@gmail.com"
         password="password"
         defaultCredentials="false"
         enableSsl="true" />
      </smtp>
   </mailSettings>
</system.net>

Yahoo Mail SMTP Settings:

<system.net>
    <mailSettings>
      <smtp>
        <network
         host="smtp.mail.yahoo.com"
         port="465"
         userName="email@yahoo.com"
         password="password"
         defaultCredentials="false"
         enableSsl="true" />
     </smtp>
   </mailSettings>
</system.net>

Razor:

if (IsPost) {
        library.SendMail("from@email.com", "to@email.com", "Subject", "Body", false);
    }