Question

I’m getting an exception randomly with the Send method shown below. The exception I’m getting is:

Exception information:
    Exception type: System.Net.Mail.SmtpException
    Exception message: Failure sending mail.

Inner exception information (level 1):
    Exception type: System.IndexOutOfRangeException
    Exception message: Index was outside the bounds of the array.

My method looks like the following:

public void Send(string from, List<string> to, string subject, string body, List<string> attachments)
{
    var email = new MailMessage();
    var server = new SmtpClient();

    // Add each mail property
    email.From = new MailAddress(from);
    foreach (var t in to)
        email.To.Add(t);
    email.Subject = subject;
    email.IsBodyHtml = true;
    email.Body = body;
    foreach (var a in attachments)
        email.Attachments.Add(new Attachment(a));
    server.Send(email);
}

Before calling this override, I’m verifying that the to List and the attachment list both have at least a single value and that the value is valid.

The exception occurs on sever.Send.

Answer 1

This sounds like the same issue as this question about .NET 4.0 failing when sending emails with large attachments. Microsoft has posted a bug fix here.