Catch SMTP Exception and re-send Email.

SmtpException Class

Represents the exception that is thrown when the SmtpClient is not able to complete a Send or SendAsync operation.
Namespace: System.Net.MailAssembly: System (in System.dll)

Code Sample

public static void RetryIfBusy(string server)
{
MailAddress from = new MailAddress("ben@contoso.com");
MailAddress to = new MailAddress("jane@contoso.com");
MailMessage message = new MailMessage(from, to);
// message.Subject = "Using the SmtpClient class.";
message.Subject = "Using the SmtpClient class.";
message.Body = @"Using this feature, you can send an e-mail message from an application very easily.";
// Add a carbon copy recipient.
MailAddress copy = new MailAddress("Notifications@contoso.com");
message.CC.Add(copy);
SmtpClient client = new SmtpClient(server);
// Include credentials if the server requires them.
client.Credentials = (ICredentialsByHost)CredentialCache.DefaultNetworkCredentials;
Console.WriteLine("Sending an e-mail message to {0} using the SMTP host {1}.",
to.Address, client.Host);
try
{
client.Send(message);
}
catch (SmtpFailedRecipientsException ex)
{
for (int i = 0; i < ex.InnerExceptions.Length; i++)
{
SmtpStatusCode status = ex.InnerExceptions[i].StatusCode;
if (status == SmtpStatusCode.MailboxBusy ||
status == SmtpStatusCode.MailboxUnavailable)
{
Console.WriteLine("Delivery failed - retrying in 5 seconds.");
System.Threading.Thread.Sleep(5000);
client.Send(message);
}
else
{
Console.WriteLine("Failed to deliver message to {0}",
ex.InnerExceptions[i].FailedRecipient);
}
}
}
catch (Exception ex)
{
Console.WriteLine("Exception caught in RetryIfBusy(): {0}",
ex.ToString() );
}
}