我可以在C＃项目中加入SMTP电子邮件“服务”吗？

Question

I've written several programs that send email from C#. This works great in winXP, but I find it breaks in Win7. My understanding is that even though the SMTP server I'm referencing is on another computer, the sending computer needs to have the SMTP service installed (and win7 does not).

I know its possible to install a third party SMTP server, but then I'd need to do that on every computer running my programs. Instead, I'd like to include a temporary SMTP server in my project that I can use entirely from code to do the same job. Does anyone know of a library (or sample code) on how I can include a temporary SMTP server in my project?

Here is my code:

public static void sendEmail(String[] recipients, String sender, String subject, String body, String[] attachments)
    {
            MailMessage message;

            try
            {
                message = new MailMessage(sender, recipients[0]);
            }
            catch (Exception)
            {
                return;
            }

            foreach (String s in recipients)
            {
                if (!message.To.Contains(new MailAddress(s)))
                    message.To.Add(s);
            }

            message.From = new MailAddress(sender);
            message.Subject = subject;
            message.Body = body;
            message.IsBodyHtml = true;
            SmtpClient smtp = new SmtpClient("PRIVATE.PRIVATE.PRIVATE", 25);
            smtp.DeliveryMethod = SmtpDeliveryMethod.PickupDirectoryFromIis;
            //smtp.DeliveryMethod = SmtpDeliveryMethod.Network;

            smtp.UseDefaultCredentials = true;

            if (attachments.Length > 0)
            {
                foreach (String a in attachments)
                {
                    message.Attachments.Add(new Attachment(a));
                }
            }
            try
            {
                smtp.SendAsync(message, null);

Answer 1

To send emails from c#, you do not need a local SMTP service. You just need the System.Net.Mail library. Using a remote SMTP server (possibly one with valid PTR settings and not one in your network to avoid being regarded as a spammer) should definitely suffice.

Answer 2

It may be a credentials issue. Change SendAsync to Send to see if you are getting any exceptions. Or add a handler for the Async invocation

smtp.SendCompleted += delegate(object s, System.ComponentModel.AsyncCompletedEventArgs    e)
{
    if (e.Error != null)
     {
        System.Diagnostics.Trace.TraceError(e.Error.ToString());
     }
};

Following changes to your code works for me in Win7

SmtpClient smtp = new SmtpClient("smtp.gmail.com", 587);
//smtp.DeliveryMethod = SmtpDeliveryMethod.PickupDirectoryFromIis;
smtp.DeliveryMethod = SmtpDeliveryMethod.Network;
smtp.Credentials = new NetworkCredential(GoogleUserEmail, GooglePassword);
smtp.EnableSsl = true;

// smtp.UseDefaultCredentials = true;

if (attachments != null && attachments.Length > 0)
        {
            foreach (String a in attachments)
            {
                message.Attachments.Add(new Attachment(a));
            }
        }
        try
        {
            smtp.Send(message);
        }

Answer 3

I have never found an embeddable SMTP server, but both of these are close and you could probably modify them to fit your needs.

http://www.codeproject.com/KB/IP/smtppop3mailserver.aspx

http://www.ericdaugherty.com/dev/cses/developers.html

I'm going to keep looking because this is also something I'd find useful. I'll post more if I find any.

Answer 4

Have you tried specifying SMTP settings in an App.config file? Something like:

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
    <system.net>
        <mailSettings>
            <smtp deliveryMethod="Network">
                <specifiedPickupDirectory pickupDirectoryLocation="C:\tmp"/>
                <network host="smtp.example.com"/>
            </smtp>
        </mailSettings>
    </system.net>
</configuration>

If you change deliveryMethod="SpecifiedPickupDirectory" then it'll just write a file representing the email that would be sent to the directory you specify.

Hope this helps.

Answer 5

If you just use an unconfigured service to send your emails you will definitely end up in the SPAM folder due to reverse DNS and SPF checks failing. So you'll want to configure your server properly. Alternatively you can use a 3rd party service like Elastic Email . Here is Elastic Email's sample code which uses HTTP to send the mail:

    public static string SendEmail(string to, string subject, string bodyText, string bodyHtml, string from, string fromName)
    {

        WebClient client = new WebClient();
        NameValueCollection values = new NameValueCollection();
        values.Add("username", USERNAME);
        values.Add("api_key", API_KEY);
        values.Add("from", from);
        values.Add("from_name", fromName);
        values.Add("subject", subject);
        if (bodyHtml != null)
            values.Add("body_html", bodyHtml);
        if (bodyText != null)
            values.Add("body_text", bodyText);
        values.Add("to", to);

        byte[] response = client.UploadValues("https://api.elasticemail.com/mailer/send", values);
        return Encoding.UTF8.GetString(response);
    }