//simple email
MailMessage mail = new MailMessage();
mail.To = "me@mycompany.com";
mail.From = "you@yourcompany.com";
mail.Subject = "this is a test email.";
mail.Body = "this is my test email body";
SmtpMail.SmtpServer = "localhost";  //your real server goes here
SmtpMail.Send( mail );

//simple Html email
MailMessage mail = new MailMessage();
mail.To = "me@mycompany.com";
mail.From = "you@yourcompany.com";
mail.Subject = "this is a test email.";
mail.BodyFormat = MailFormat.Html;
mail.Body = "this is my test email body.<br><b>this part is in bold</b>";
SmtpMail.SmtpServer = "localhost";  //your real server goes here
SmtpMail.Send( mail );

//email with attachments

MailMessage mail = new MailMessage();
mail.To = "me@mycompany.com";
mail.From = "you@yourcompany.com";
mail.Subject = "this is a test email.";
mail.Body = "this is my test email body.";
MailAttachment attachment = new MailAttachment( Server.MapPath( "test.txt" ) ); //create the attachment
mail.Attachments.Add( attachment ); //add the attachment
SmtpMail.SmtpServer = "localhost";  //your real server goes here
SmtpMail.Send( mail );

//change the TO address to a friendly name
mail.From = "\"John Smith\" <you@yourcompany.com>";

//multiple recipients
mail.To = "me@mycompany.com;him@hiscompany.com;her@hercompany.com";