Sending mail using Sharepoint

string smtpServer = SPAdministrationWebApplication.Local.OutboundMailServiceInstance.Server.Address;
string smtpFrom = SPAdministrationWebApplication.Local.OutboundMailSenderAddress;
MailMessage message = new MailMessage(smtpFrom, "test@gmail.com");
//MailMessage message = new MailMessage(smtpFrom, "test@gmail.com");
message.Subject = "Happy Birthday";
WebClient client = new WebClient();
client.Credentials = CredentialCache.DefaultNetworkCredentials;

string imagePath = web.Url + "/_layouts/images/BirthdayImage.gif";
LinkedResource image1 = new LinkedResource(SPUtility.GetGenericSetupPath("TEMPLATE\\LAYOUTS\\IMAGES\\BirthdayImage.gif"));
image1.ContentId = "birthdayimage";
AlternateView avHtml = AlternateView.CreateAlternateViewFromString("
" + "Have a blast with frineds and family!!! Have a great day!!!", null, MediaTypeNames.Text.Html);
avHtml.LinkedResources.Add(image1);
message.AlternateViews.Add(avHtml);
message.IsBodyHtml = true;

SmtpClient smtpClient = new SmtpClient(smtpServer);
smtpClient.Send(message);