带有 Gmail 的 SmtpClient

Question

我正在为一个学校项目开发一个邮件客户端。我已经设法在 C# 中使用SmtpClient 发送电子邮件。这适用于任何服务器，但不适用于 Gmail。我相信这是因为谷歌使用了 TLS。我尝试在SmtpClient 上将EnableSsl 设置为true，但这并没有什么不同。

这是我用来创建SmtpClient 并发送电子邮件的代码。

this.client = new SmtpClient("smtp.gmail.com", 587);
this.client.EnableSsl = true;
this.client.UseDefaultCredentials = false;
this.client.Credentials = new NetworkCredential("username", "password");

try
{
    // Create instance of message
    MailMessage message = new MailMessage();

    // Add receiver
    message.To.Add("myemail@mydomain.com");

    // Set sender
    // In this case the same as the username
    message.From = new MailAddress("username@gmail.com");

    // Set subject
    message.Subject = "Test";

    // Set body of message
    message.Body = "En test besked";

    // Send the message
    this.client.Send(message);

    // Clean up
    message = null;
}
catch (Exception e)
{
    Console.WriteLine("Could not send e-mail. Exception caught: " + e);
}

这是我在尝试发送电子邮件时遇到的错误。

Could not send e-mail. Exception caught: System.Net.Mail.SmtpException: Message could not be sent. ---> System.IO.IOException: The authentication or decryption has failed. ---> System.InvalidOperationException: SSL authentication error: RemoteCertificateNotAvailable, RemoteCertificateChainErrors
  at System.Net.Mail.SmtpClient.<callback>m__4 (System.Object sender, System.Security.Cryptography.X509Certificates.X509Certificate certificate, System.Security.Cryptography.X509Certificates.X509Chain chain, SslPolicyErrors sslPolicyErrors) [0x00000] in <filename unknown>:0 
  at System.Net.Security.SslStream+<BeginAuthenticateAsClient>c__AnonStorey7.<>m__A (System.Security.Cryptography.X509Certificates.X509Certificate cert, System.Int32[] certErrors) [0x00000] in <filename unknown>:0 
  at Mono.Security.Protocol.Tls.SslClientStream.OnRemoteCertificateValidation (System.Security.Cryptography.X509Certificates.X509Certificate certificate, System.Int32[] errors) [0x00000] in <filename unknown>:0 
  at Mono.Security.Protocol.Tls.SslStreamBase.RaiseRemoteCertificateValidation (System.Security.Cryptography.X509Certificates.X509Certificate certificate, System.Int32[] errors) [0x00000] in <filename unknown>:0 
  at Mono.Security.Protocol.Tls.SslClientStream.RaiseServerCertificateValidation (System.Security.Cryptography.X509Certificates.X509Certificate certificate, System.Int32[] certificateErrors) [0x00000] in <filename unknown>:0 
  at Mono.Security.Protocol.Tls.Handshake.Client.TlsServerCertificate.validateCertificates (Mono.Security.X509.X509CertificateCollection certificates) [0x00000] in <filename unknown>:0 
  at Mono.Security.Protocol.Tls.Handshake.Client.TlsServerCertificate.ProcessAsTls1 () [0x00000] in <filename unknown>:0 
  at Mono.Security.Protocol.Tls.Handshake.HandshakeMessage.Process () [0x00000] in <filename unknown>:0 
  at (wrapper remoting-invoke-with-check) Mono.Security.Protocol.Tls.Handshake.HandshakeMessage:Process ()
  at Mono.Security.Protocol.Tls.ClientRecordProtocol.ProcessHandshakeMessage (Mono.Security.Protocol.Tls.TlsStream handMsg) [0x00000] in <filename unknown>:0 
  at Mono.Security.Protocol.Tls.RecordProtocol.InternalReceiveRecordCallback (IAsyncResult asyncResult) [0x00000] in <filename unknown>:0 
  --- End of inner exception stack trace ---
  at Mono.Security.Protocol.Tls.SslStreamBase.AsyncHandshakeCallback (IAsyncResult asyncResult) [0x00000] in <filename unknown>:0 
  --- End of inner exception stack trace ---
  at System.Net.Mail.SmtpClient.Send (System.Net.Mail.MailMessage message) [0x00000] in <filename unknown>:0 
  at P2Mailclient.SMTPClient.send (P2Mailclient.Email email) [0x00089] in /path/to/my/project/SMTPClient.cs:57 

有人知道我为什么会收到这个错误吗？

Answer 1

Gmail 的 SMTP 服务器要求您使用有效的 gmail 电子邮件/密码组合来验证您的请求。您还需要启用 SSL。如果实际上无法看到传递的所有变量的转储，我可以做出的最佳猜测是您的凭据无效，请确保您使用的是有效的 GMAIL 电子邮件/密码组合。

您可能想阅读here 以了解一个工作示例。

编辑：好的，这是我当时编写和测试的东西，对我来说效果很好：

public static bool SendGmail(string subject, string content, string[] recipients, string from) {
    if (recipients == null || recipients.Length == 0)
        throw new ArgumentException("recipients");

    var gmailClient = new System.Net.Mail.SmtpClient {
        Host = "smtp.gmail.com",
        Port = 587,
        EnableSsl = true,
        UseDefaultCredentials = false,
        Credentials = new System.Net.NetworkCredential("******", "*****")
    };

    using (var msg = new System.Net.Mail.MailMessage(from, recipients[0], subject, content)) {
        for (int i = 1; i < recipients.Length; i++)
            msg.To.Add(recipients[i]);

        try {
            gmailClient.Send(msg);
            return true;
        }
        catch (Exception) {
            // TODO: Handle the exception
            return false;
        }
    }
}

如果您需要更多信息，请参阅类似的 SO 文章 here

Answer 2

这段代码对我来说很好用，尝试将其粘贴到 LinqPad 中，编辑邮件地址和密码，然后告诉我们你看到了什么：

var client = new System.Net.Mail.SmtpClient("smtp.gmail.com", 587);
client.EnableSsl = true;
client.UseDefaultCredentials = false;
client.Credentials = new System.Net.NetworkCredential("me@gmail.com", "xxxxxxx");

try
{
    // Create instance of message
    System.Net.Mail.MailMessage message = new System.Net.Mail.MailMessage();

    // Add receiver
    message.To.Add("me@gmail.com");

    // Set sender
    // In this case the same as the username
    message.From = new System.Net.Mail.MailAddress("me@gmail.com");

    // Set subject
    message.Subject = "Test";

    // Set body of message
    message.Body = "En test besked";

    // Send the message
    client.Send(message);

    // Clean up
    message = null;
}
catch (Exception e)
{
    Console.WriteLine("Could not send e-mail. Exception caught: " + e);
}

Answer 3

我认为，您需要验证用于建立 SSL 连接的服务器证书.....

使用以下代码发送带有验证服务器证书的邮件.....

            this.client = new SmtpClient(_account.SmtpHost, _account.SmtpPort);
            this.client.EnableSsl = _account.SmtpUseSSL;
            this.client.Credentials = new NetworkCredential(_account.Username, _account.Password);

        try
        {
            // Create instance of message
            MailMessage message = new MailMessage();

            // Add receivers
            for (int i = 0; i < email.Receivers.Count; i++)
                message.To.Add(email.Receivers[i]);

            // Set sender
            message.From = new MailAddress(email.Sender);

            // Set subject
            message.Subject = email.Subject;

            // Send e-mail in HTML
            message.IsBodyHtml = email.IsBodyHtml;

            // Set body of message
            message.Body = email.Message;

            //validate the certificate
            ServicePointManager.ServerCertificateValidationCallback =
            delegate(object s, X509Certificate certificate, X509Chain chain, SslPolicyErrors sslPolicyErrors)
            { return true; };


            // Send the message
            this.client.Send(message);

            // Clean up
            message = null;
        }
        catch (Exception e)
        {
            Console.WriteLine("Could not send e-mail. Exception caught: " + e);
        }

导入System.Security.Cryptography.X509Certificates命名空间以使用ServicePointManager

Answer 4

尝试运行这个：

mozroots --import --ask-remove

在您的系统中（如果在 Windows 上，则仅在 bash 或 Mono 命令提示符中）。然后再次运行代码。

编辑：

我忘了你也应该跑

certmgr -ssl smtps://smtp.gmail.com:465

（并对问题回答是）。这适用于我在 Mono 2.10.8、Linux 上（以您的示例为例）。

Answer 5

在工作了 6 个月后，我于 2013 年 5 月开始使用 GMail 获取此信息。 Mono 项目的Using Trusted Roots Respectfully 文档提供了解决方法的指导。我选择了选项 #1：

ServicePointManager.ServerCertificateValidationCallback = delegate { return true; };

让我的服务在没有警告的情况下停止工作的电子邮件太具有破坏性了。

2016 年 8 月 26 日更新：用户 Chico 建议以下完整实现 ServerCertificateValidationCallback 回调。我没有测试过。

ServicePointManager.ServerCertificateValidationCallback = MyRemoteCertificateValidationCallback;

bool MyRemoteCertificateValidationCallback(System.Object sender, X509Certificate certificate, X509Chain chain, SslPolicyErrors sslPolicyErrors) {
    bool isOk = true;
    // If there are errors in the certificate chain, look at each error to determine the cause.
    if (sslPolicyErrors != SslPolicyErrors.None) {
        for (int i=0; i<chain.ChainStatus.Length; i++) {
            if (chain.ChainStatus [i].Status != X509ChainStatusFlags.RevocationStatusUnknown) {
                chain.ChainPolicy.RevocationFlag = X509RevocationFlag.EntireChain;
                chain.ChainPolicy.RevocationMode = X509RevocationMode.Online;
                chain.ChainPolicy.UrlRetrievalTimeout = new TimeSpan (0, 1, 0);
                chain.ChainPolicy.VerificationFlags = X509VerificationFlags.AllFlags;
                bool chainIsValid = chain.Build ((X509Certificate2)certificate);
                if (!chainIsValid) {
                    isOk = false;
                }
            }
        }
    }
    return isOk;

}

Answer 6

您需要在您的 gmail 帐户中启用两步验证并创建一个应用密码 (https://support.google.com/accounts/answer/185833?hl=en)。将密码替换为新的应用密码后，它应该可以工作。

Credentials = new System.Net.NetworkCredential("your email address", "your app password");