How to email large files using c# windows application

问题

I'm developing an windows application in which i need to send some files as attachment through email.

Code

public string SendMail(string mFrom,
        string mPass,
        string mTo,
        string mSub,
        string mMsg,
        string mFile,
        bool isDel)
    {
        string sql = "";
        try
        {
            System.Net.Mail.MailAddress mailfrom = new System.Net.Mail.MailAddress(mFrom);
            System.Net.Mail.MailAddress mailto = new System.Net.Mail.MailAddress(mTo);
            System.Net.Mail.MailMessage newmsg = new System.Net.Mail.MailMessage(mailfrom, mailto);
            newmsg.IsBodyHtml = false;
            if (mFile.Length > 2
                && File.Exists(mFile))
            {
                System.Net.Mail.Attachment att = new System.Net.Mail.Attachment(mFile);
                newmsg.Attachments.Add(att);
            }
            newmsg.Subject = mSub;
            newmsg.Body = mMsg;
            System.Net.Mail.SmtpClient smtp = new System.Net.Mail.SmtpClient("smtp.gmail.com", 587);
            smtp.UseDefaultCredentials = false;
            smtp.Credentials = new System.Net.NetworkCredential(mFrom, mPass);
            smtp.EnableSsl = true;
            smtp.Send(newmsg);
            newmsg.Dispose();
            GC.Collect();
            sql = "OK";
            if (isDel
                && File.Exists(mFile))
            {
                File.Delete(mFile);
            }
        }
        catch (Exception ex)
        {
            sql = ex.Message;
        }
        return sql;
    }

This code works fine for small files.But i need to send large files up to 1-2 GB. For that what to do.

回答1:

You cannot use e-mail to get these files across and this has nothing to do with your code.

I don't think there is ANY provider out there who will support sending files of that size let alone receiving them. Even G-Mail has a limit of 25 Mb which is quite large already.

E-Mail is not the proper channel to do this.

So the problem will not be in your code, the provider will limit the size of the attachment and just refuse them when you present them with a larger file. You will get an e-mail back at your FROM address stating that the file is too large and your e-mail did not get across.

For doing this in the simplest form probably look at FTP.

回答2:

I do agree with Gerald Versluis in that email is not the proper channel for this. Even if you are using your own email server that is configurable there is probably some internal limit that prevents it from sending such big files.

I’d go with FTP for this but if you really want to continue with email I’d suggest you check following first.

Is there connection timeout property on the server? If yes then try to increase it to 3 hours or something like that.
Is there enough space on the mail server?
Is there some documentation for your email server? Are there any additional details regarding attachment size ?

来源：https://stackoverflow.com/questions/16684941/how-to-email-large-files-using-c-sharp-windows-application

标签

winforms

large-files