使用 MailKit 向 SpecifiedPickupDirectory 发送电子邮件

Question

到目前为止，我一直在使用 SmtpClient 和 ASP.NET MVC 5。为了在本地系统上测试电子邮件发送功能，我使用的是 client.DeliveryMethod = SmtpDeliveryMethod.SpecifiedPickupDirectory;

现在，我想在目前还没有实现 SmtpClient 类的 ASP.NET Core 中做同样的事情。对此的所有搜索都以MailKit 结束。我使用了他们的发送邮件代码，该代码在 gmail 上运行良好。

我不想每次都发送测试邮件，我的项目中可能有很多场景需要发送邮件。如何通过 MailKit 使用本地电子邮件发送功能。任何链接或少量源代码都会有所帮助。谢谢

Answer 1

我不确定SmtpDeliveryMethod.SpecifiedPickupDirectory 的工作原理和具体作用的详细信息，但我怀疑它可能只是将邮件保存在本地 Exchange 服务器定期检查要发送的邮件的目录中。

假设是这样，你可以这样做：

public static void SaveToPickupDirectory (MimeMessage message, string pickupDirectory)
{
    do {
        // Generate a random file name to save the message to.
        var path = Path.Combine (pickupDirectory, Guid.NewGuid ().ToString () + ".eml");
        Stream stream;

        try {
            // Attempt to create the new file.
            stream = File.Open (path, FileMode.CreateNew);
        } catch (IOException) {
            // If the file already exists, try again with a new Guid.
            if (File.Exists (path))
                continue;

            // Otherwise, fail immediately since it probably means that there is
            // no graceful way to recover from this error.
            throw;
        }

        try {
            using (stream) {
                // IIS pickup directories expect the message to be "byte-stuffed"
                // which means that lines beginning with "." need to be escaped
                // by adding an extra "." to the beginning of the line.
                //
                // Use an SmtpDataFilter "byte-stuff" the message as it is written
                // to the file stream. This is the same process that an SmtpClient
                // would use when sending the message in a `DATA` command.
                using (var filtered = new FilteredStream (stream)) {
                    filtered.Add (new SmtpDataFilter ());

                    // Make sure to write the message in DOS (<CR><LF>) format.
                    var options = FormatOptions.Default.Clone ();
                    options.NewLineFormat = NewLineFormat.Dos;

                    message.WriteTo (options, filtered);
                    filtered.Flush ();
                    return;
                }
            }
        } catch {
            // An exception here probably means that the disk is full.
            //
            // Delete the file that was created above so that incomplete files are not
            // left behind for IIS to send accidentally.
            File.Delete (path);
            throw;
        }
    } while (true);
}

上面的代码 sn-p 使用Guid.NewGuid () 作为生成临时文件名的一种方式，但您可以使用任何您想要的方法（例如，您也可以选择使用message.MessageId + ".eml"）。

基于微软的referencesource，当使用SpecifiedPickupDirectory时，他们实际上也使用Guid.NewGuid ().ToString () + ".eml"，所以这可能是要走的路。