操作已超时-SMTP邮件-多个收件人

Question

this is my scenario: I'm trying to send mail with SMTP client, when I try to send the mail to max 3 recipient, that worked perfectly, but, when the recipients number is higher than 3, it return "Operation has timed out".

 MailMessage mail = new MailMessage();
 SmtpClient smtpServer;
 if ((smtpPort != null) && (smtpPort != string.Empty))
        smtpServer = new SmtpClient(smtpAddress, getInt(smtpPort,25));
            else
                            smtpServer = new SmtpClient(smtpAddress);
                        mail.From = new System.Net.Mail.MailAddress(senderAddress, senderName);
                        if (null != to)
                            foreach (string toElement in to)
                                mail.To.Add(toElement);
                        if (null != cc)
                            foreach (string ccElement in cc)
                                mail.CC.Add(ccElement);
                        if (null != bcc)
                            foreach (string bccElement in bcc)
                                mail.Bcc.Add(bccElement);
                        mail.Subject = subjectString;
                        mail.Body = message;

                        if (mailFilename != null)
                        {
                            System.Net.Mail.Attachment attachment;
                            foreach (string path in mailFilename)
                                if (System.IO.File.Exists(eMailPath.Replace("timestamp", path) + path + ".eml"))
                                {
                                    attachment = new System.Net.Mail.Attachment(eMailPath.Replace("timestamp", path) + path + ".eml");
                                    mail.Attachments.Add(attachment);
                                }
                        }
                        smtpServer.Send(mail);
     }

Question Can I split sending so that the multiple recipients can see other recipients as if the sending is one?

Example

Recipients list: a@dom.it, b@dom.it, c@dom.it, mailingList@dom.it --> the mailing list is composed by 4 recipients.

Original send: To: mailingList@dom.it CC:a@dom.it,b@dom.it BCC:c@dom.it

I want to split sending in way that the various recipients can see other recipients like the original sending.

Answer 1

I don't see anywhere that you're setting the .Host property on the SMTPClient object. So, it's probably sending out through the local SMTP server by default, and I'm guessing that you may be hitting some limit on this local SMTP server, or it's throttling, or something of that sort. Perhaps using the .Host property to route these outgoing messages through some other SMTP server (eg smtp.gmail.com) might solve the problem.