How to send email from Asp.net Mvc-3?

Import the System.Net.Mail namespace.

The code will look similar to this:

MailMessage mail = new MailMessage();

SmtpClient smtpServer = new SmtpClient("smtp.gmail.com");
smtpServer.Credentials = new System.Net.NetworkCredential("userName", "password");
smtpServer.Port = 587; // Gmail works on this port

mail.From = new MailAddress("myemail@gmail.com");
mail.To.Add("recepient@gmail.com");
mail.Subject = "Password recovery";
mail.Body = "Recovering the password";

smtpServer.Send(mail);

P.S. You have a SQL injection vulnerability in the sample code. Use a SqlCommand object with parameters instead of String.Format().

Using SqlDataReader would be a lot more efficient to check for a record instead of populating a DataSet.