Email failure when one email is wrong in same domain in asp.net

Question

I have one "Email" function in my project.if all email ids are correct in same domain , email will send successfully. if one of the email is wrong then email will fail and get below error.

Exception:-The server rejected one or more recipient addresses. The server response was: 550 5.0.0 Requested action not taken: mailbox unavailable or not local.  , InnerException:-System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ---> System.Runtime.InteropServices.COMException: The server rejected one or more recipient addresses. The server response was: 550 5.0.0 Requested action not taken: mailbox unavailable or not local.       --- End of inner exception stack trace ---     at System.RuntimeType.InvokeDispMethod(String name, BindingFlags invokeAttr, Object target, Object[] args, Boolean[] byrefModifiers, Int32 culture, String[] namedParameters)     at System.RuntimeType.InvokeMember(String name, BindingFlags bindingFlags, Binder binder, Object target, Object[] providedArgs, ParameterModifier[] modifiers, CultureInfo culture, String[] namedParams)     at System.Web.Mail.SmtpMail.LateBoundAccessHelper.CallMethod(Object obj, String methodName, Object[] args) , Stack Trace :-   at System.Web.Mail.SmtpMail.LateBoundAccessHelper.CallMethod(Object obj, String methodName, Object[] args)     at System.Web.Mail.SmtpMail.CdoSysHelper.Send(MailMessage message)     at System.Web.Mail.SmtpMail.Send(MailMessage message)     at Entity.Common.Mail.SendMail(String mailFrom, String mailTo, String mailCc, String Subject, String Content, String Bcc, String optionalfrom)

code follows

MailAddress xfrom = new MailAddress(EmailFrom);
        MailMessage mm = new MailMessage();
        mm.Sender = xfrom;
        mm.From = xfrom;

        //to
        string[] tos = EmailTO.Trim().Split(';');
        for (int i = 0; i < tos.Length; i++)
        {
            mm.To.Add(new MailAddress(tos[i]));
        }
        SmtpClient smtp = new SmtpClient();
        smtp.Host = smtpServer;
        smtp.Credentials = new NetworkCredential(smtpMailAccount, smtpMailPassword);
        smtp.Send(mm);
        IsSuccess = true;

How to ignore the wrong email id and send email to rest all correct email ids ? i want to send email even wrong email id is exists. how to solve this issue? help / suggestion appreciated.

Answer 1

Catch the exception as a SmtpFailedRecipientException, which has a property FailedRecipient. Remove this one from the To collection, and retry until no more SmtpFailedRecipientException is thrown.

A small excerpt of a project where I did just that, note that there is also a plural version of that exception, which can contain more than one failed recipient in its InnerExceptions list:

try
{
    /* code to send */
}
catch (SmtpFailedRecipientsException recsex)
{
    var failedRecipient = String.Empty;
    foreach (var rex in recsex.InnerExceptions)
    {
        /* rex.FailedRecipient contains the invalid address to remove
         * before the next attempt.
         * note that you might end up with an empty recipient list
         * in case all were invalid, then you should also no longer
         * attemtp to resubmit the mail */
    }
}
catch (SmtpFailedRecipientException recex)
{
    /* recex.FailedRecipient contains the invalid address to remove
     * before the next attempt */
}