MailMessage message = new MailMessage();
message.From = new MailAddress("from@server.com", "From Name");

message.To.Add(new MailAddress("to1@server.com", "Name One"));
message.To.Add(new MailAddress("to2@server.com", "Name Two"));
message.CC.Add(new MailAddress("cc@server.com", "CC Name"));
message.Bcc.Add(new MailAddress("bcc@server.com", "BCC Name"));

message.Subject = "Subject";
message.Body = "This is a plain text";
message.IsBodyHtml = false;

SmtpClient emailClient = new SmtpClient("mail.server.com");
emailClient.Send(message);