c# - GMAIL SMTP : A call to SSPI failed exception - The function requested is not supported

Question

我正在使用 gmail smtp 发送邮件:主机:smtp.gmail.com端口:587

在 MVC 应用程序中使用 gmail smtp 发送邮件时出现异常。以下代码用于发送邮件:

public static int SendMail(string StrFromAdd, string StrEmailTo, string StrSubject, string StrContents,
        string SMTPServer, int SMTPPort, string SMTPUserName, string SMTPPassword,
        string attachment = "", string CC = "", string BCC = "")
    {
        try
        {
            AlternateView AV = null;
            System.Net.Mail.SmtpClient smtpClient = new System.Net.Mail.SmtpClient();
            System.Net.Mail.MailMessage message = new System.Net.Mail.MailMessage();
            System.Net.Mail.MailAddress fromAddress = new System.Net.Mail.MailAddress(StrFromAdd, "Test");
            smtpClient.Host = SMTPServer;
            smtpClient.Port = SMTPPort;
            smtpClient.Credentials = new System.Net.NetworkCredential(SMTPUserName, SMTPPassword);

            smtpClient.EnableSsl = true;

            message.From = fromAddress;

            if (attachment != null)
            {
                string[] attachmentsarr = attachment.Split(';');
                foreach (string attach in attachmentsarr)
                {
                    if (attach != "")
                        message.Attachments.Add(new Attachment(attach));
                }
            }

            string pattern = @"^((([\w]+\.[\w]+)+)|([\w]+))@(([\w]+\.)+)([A-Za-z]{1,3})$";

            if (StrEmailTo != "")
            {
                if (StrEmailTo.IndexOf(',') > -1)
                {
                    string[] _strArrstrEmailTo = StrEmailTo.Split(',');
                    foreach (object objBCCEmailID in _strArrstrEmailTo)
                        if (Regex.IsMatch(objBCCEmailID.ToString().Trim(), pattern))
                            message.To.Add(new System.Net.Mail.MailAddress(objBCCEmailID.ToString().Trim()));

                }
                else
                    message.To.Add(new System.Net.Mail.MailAddress(StrEmailTo.ToString().Trim()));
            }

            if (CC != "")
            {
                if (CC.IndexOf(',') > -1)
                {
                    string[] _strArrstrEmailCC = CC.Split(',');
                    foreach (object objBCCEmailID in _strArrstrEmailCC)
                        if (Regex.IsMatch(objBCCEmailID.ToString().Trim(), pattern))
                            message.CC.Add(new System.Net.Mail.MailAddress(objBCCEmailID.ToString().Trim()));

                }
                else
                    message.CC.Add(new System.Net.Mail.MailAddress(CC.ToString().Trim()));
            }

            if (BCC != "")
            {
                if (BCC.IndexOf(',') > -1)
                {
                    string[] _strArrstrEmailBCC = BCC.Split(',');
                    foreach (object objBCCEmailID in _strArrstrEmailBCC)
                        if (Regex.IsMatch(objBCCEmailID.ToString().Trim(), pattern))
                            message.Bcc.Add(new System.Net.Mail.MailAddress(objBCCEmailID.ToString().Trim()));

                }
                else
                    message.Bcc.Add(new System.Net.Mail.MailAddress(BCC.ToString().Trim()));
            }
            // This is added for custom form & email template image
            List<string> ImageFiles = Common.GetImagesInHTMLString(StrContents);
            if (ImageFiles != null && ImageFiles.Count > 0)
            {
                string addStrContents = string.Empty;

                for (int i = 0; i < ImageFiles.Count; i++)
                {
                    // this is for custom form
                    if (ImageFiles[i].Contains("CustomFormImage"))
                    {
                        string Path = Regex.Match(ImageFiles[i], "<img.+?src=[\"'](.+?)[\"'].+?>", RegexOptions.IgnoreCase).Groups[1].Value;
                        int pos = Path.LastIndexOf("\\") + 1;
                        string FullPath = HttpContext.Current.Server.MapPath("~/img/CustomFormImage/" + Path.Substring(pos, Path.Length - pos));
                        if (System.IO.File.Exists(FullPath))
                        {
                            //addStrContents = addStrContents + "<img style='width:100px;height:100px;' src=\"cid:" + Path.Substring(pos, Path.Length - pos).Split('.')[0] + "\">" + Environment.NewLine;
                            StrContents = StrContents.Replace(Path, "cid:" + Path.Substring(pos, Path.Length - pos).Split('.')[0]);
                        }
                    }
                    // this is for email template image
                    else if (ImageFiles[i].Contains("EmailHeaderFooterImgs"))
                    {
                        string Path = Regex.Match(ImageFiles[i], "<img.+?src =[\"'](.+?)[\"'].+?>", RegexOptions.IgnoreCase).Groups[1].Value;
                        int pos = Path.LastIndexOf("\\") + 1;
                        if (System.IO.File.Exists(Path))
                        {
                            //addStrContents = addStrContents + "<img style='width:100px;height:100px;' src=\"cid:" + Path.Substring(pos, Path.Length - pos).Split('.')[0] + "\">" + Environment.NewLine;
                            StrContents = StrContents.Replace(Path, "cid:" + Path.Substring(pos, Path.Length - pos).Split('.')[0]);
                        }
                    }
                }
                AV = AlternateView.CreateAlternateViewFromString(StrContents, null, MediaTypeNames.Text.Html);
                for (int i = 0; i < ImageFiles.Count; i++)
                {
                    // this is for custom form
                    if (ImageFiles[i].Contains("CustomFormImage"))
                    {
                        string Path = Regex.Match(ImageFiles[i], "<img.+?src=[\"'](.+?)[\"'].+?>", RegexOptions.IgnoreCase).Groups[1].Value;
                        int pos = Path.LastIndexOf("\\") + 1;
                        string FullPath = HttpContext.Current.Server.MapPath("~/img/CustomFormImage/" + Path.Substring(pos, Path.Length - pos));
                        if (System.IO.File.Exists(FullPath))
                        {
                            //FileStream fs = new FileStream(FullPath, FileMode.Open, FileAccess.Read);
                            //Attachment a = new Attachment(fs, Path.Substring(pos, Path.Length - pos), MediaTypeNames.Application.Octet);
                            //message.Attachments.Add(a);
                            //addStrContents = addStrContents + "<img src=\"cid:" + Path.Substring(pos, Path.Length - pos).Split('.')[0] + "\">" + Environment.NewLine;
                            LinkedResource Img = new LinkedResource(FullPath, MediaTypeNames.Image.Jpeg);
                            Img.ContentId = Path.Substring(pos, Path.Length - pos).Split('.')[0];
                            AV.LinkedResources.Add(Img);
                        }
                    }
                    // this is for email template image
                    else if (ImageFiles[i].Contains("EmailHeaderFooterImgs"))
                    {
                        string Path = Regex.Match(ImageFiles[i], "<img.+?src =[\"'](.+?)[\"'].+?>", RegexOptions.IgnoreCase).Groups[1].Value;
                        int pos = Path.LastIndexOf("\\") + 1;
                        if (HttpContext.Current != null)
                        {
                            string FullPath = HttpContext.Current.Server.MapPath("~/EmailHeaderFooterImgs/" + Path.Substring(pos, Path.Length - pos));
                            if (System.IO.File.Exists(Path))
                            {
                                LinkedResource Img = new LinkedResource(Path, MediaTypeNames.Image.Jpeg);
                                Img.ContentId = Path.Substring(pos, Path.Length - pos).Split('.')[0];
                                AV.LinkedResources.Add(Img);
                            }
                        }
                    }
                }
            }

            message.Subject = StrSubject;
            message.IsBodyHtml = true;
            if (AV != null)
                message.AlternateViews.Add(AV);
            else
                message.Body = StrContents;

            smtpClient.Send(message);
            message.Dispose();
            return 1;
        }
        catch (Exception ex)
        {

        }
    }

下面是堆栈轨迹:

    System.Security.Authentication.AuthenticationException: A call to SSPI failed, see inner exception. System.ComponentModel.Win32Exception: The function requested is not supported
   at System.Net.Security.SslState.StartSendAuthResetSignal(ProtocolToken message, AsyncProtocolRequest asyncRequest, Exception exception)
   at System.Net.Security.SslState.CheckCompletionBeforeNextReceive(ProtocolToken message, AsyncProtocolRequest asyncRequest)
   at System.Net.Security.SslState.ProcessReceivedBlob(Byte[] buffer, Int32 count, AsyncProtocolRequest asyncRequest)
   at System.Net.Security.SslState.StartReceiveBlob(Byte[] buffer, AsyncProtocolRequest asyncRequest)
   at System.Net.Security.SslState.CheckCompletionBeforeNextReceive(ProtocolToken message, AsyncProtocolRequest asyncRequest)
   at System.Net.Security.SslState.ForceAuthentication(Boolean receiveFirst, Byte[] buffer, AsyncProtocolRequest asyncRequest)
   at System.Net.Security.SslState.ProcessAuthentication(LazyAsyncResult lazyResult)
   at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
   at System.Net.TlsStream.ProcessAuthentication(LazyAsyncResult result)
   at System.Net.TlsStream.Write(Byte[] buffer, Int32 offset, Int32 size)
   at System.Net.Mail.SmtpConnection.Flush()
   at System.Net.Mail.ReadLinesCommand.Send(SmtpConnection conn)
   at System.Net.Mail.EHelloCommand.Send(SmtpConnection conn, String domain)
   at System.Net.Mail.SmtpConnection.GetConnection(ServicePoint servicePoint)
   at System.Net.Mail.SmtpClient.GetConnection()
   at System.Net.Mail.SmtpClient.Send(MailMessage message)
   at MVC.Common.SendMails.SendMail(String StrFromAdd, String StrEmailTo, String StrSubject, String StrContents, String SMTPServer, Int32 SMTPPort, String SMTPUserName, String SMTPPassword, String attachment, String CC, String BCC) in SendMails.cs:line 296

注意:相同的代码在托管在同一服务器上的另一个应用程序中运行，也使用相同的 gmail 配置来发送邮件。

Answer 1

假设您的代码是为(例如).NET Framework 4.7.2 编译的，那么请确保您的 Web.config 包括:

<httpRuntime targetFramework="4.7.2" />

如果您的 targetFramework 设置太低或缺失，则编译后的代码将自动尝试请求 TLS 1.2(发生在 .NET Framework 4.7 以上)，但目标运行时将不支持它，因此出现错误。

(归功于 this SO answer，这让我意识到这里出了什么问题——尽管那个问题和这个问题并不重复。)