无法使用 c# SmtpClient 从 Office 365 发送电子邮件

Question

尝试使用SmtpClient从我的c# winforms应用程序发送电子邮件。根据这篇MS文章来看，这应该是可行的。我已经搜索了许多论坛等，没有找到任何解决方案。错误消息似乎表明客户端未通过身份验证。密码是正确的，我已经用这个密码登录了。2FA是开着的，但是它不应该妨碍我们，不是吗？

我查过的东西都到位了

1. 启用SSl
2. 来自电子邮件和用户电子邮件是相同的
3. 端口587
4. 我在Outlook中有这个帐户，它发送得很好
5. 防火墙没有阻止此端口。我有其他代码在非O365主机上使用完全相同的代码，它工作正常

法典

            var userName = "[e-mail]";
            var password = "password";
            var msg = new MailMessage();
            msg.To.Add(new MailAddress("[e-mail]"));
            msg.From = new MailAddress(userName);
            msg.Subject = "Test Office 365 Account";
            msg.Body = "Testing email using Office 365 account.";
            msg.IsBodyHtml = true;

            var client = new SmtpClient{
                Host = "smtp.office365.com",
                Credentials = new System.Net.NetworkCredential(userName, password),
                Port = 587,
                DeliveryMethod = SmtpDeliveryMethod.Network,
                EnableSsl = true
            };

            client.Send(msg);

例外情况

• SMTP 服务器需要安全连接，或者客户端未经过身份验证。服务器响应为：5.7.57 SMTP;客户端未通过身份验证以在邮件发件人期间发送匿名邮件

邮件工具包实施（vasily.sib建议）

var message = new MimeMessage();
        message.From.Add(new MailboxAddress("Test User", "[e-mail]"));
        message.To.Add(new MailboxAddress("Gmail User", "[e-mail]"));
        message.Subject = "test";

        message.Body = new TextPart("plain")
        {
            Text = @"test"
        };

        var client = new SmtpClient(new ProtocolLogger("imap.log"));


        // For demo-purposes, accept all SSL certificates (in case the server supports STARTTLS)
        client.ServerCertificateValidationCallback = (s, c, h, e) => true;

        client.Connect("smtp.office365.com", 587, SecureSocketOptions.Auto); //this is fine and it connects

        var clientAuthenticationMechanisms = client.AuthenticationMechanisms;
        client.AuthenticationMechanisms.Remove("XOAUTH2");
        // Note: only needed if the SMTP server requires authentication
        client.Authenticate("[e-mail]", "password"); // this is where it fails with Authentication Failure

        client.Send(message);
        client.Disconnect(true);

邮件工具包日志输出

Connected to smtp://smtp.office365.com:587/?starttls=when-available
S: 220 SYCP282CA0015.outlook.office365.com Microsoft ESMTP MAIL Service ready at Mon, 25 Nov 2019 04:49:36 +0000
C: EHLO [192.168.2.50]
S: 250-SYCP282CA0015.outlook.office365.com Hello [58.6.92.82]
S: 250-SIZE 157286400
S: 250-PIPELINING
S: 250-DSN
S: 250-ENHANCEDSTATUSCODES
S: 250-STARTTLS
S: 250-8BITMIME
S: 250-BINARYMIME
S: 250-CHUNKING
S: 250 SMTPUTF8
C: STARTTLS
S: 220 2.0.0 SMTP server ready
C: EHLO [192.168.2.50]
S: 250-SYCP282CA0015.outlook.office365.com Hello [58.6.92.82]
S: 250-SIZE 157286400
S: 250-PIPELINING
S: 250-DSN
S: 250-ENHANCEDSTATUSCODES
S: 250-AUTH LOGIN XOAUTH2
S: 250-8BITMIME
S: 250-BINARYMIME
S: 250-CHUNKING
S: 250 SMTPUTF8
C: AUTH LOGIN
REMOVED BASE64 DATA (password, login)
S: 535 5.7.3 Authentication unsuccessful [SYCP282CA0015.AUSP282.PROD.OUTLOOK.COM]

Answer 1

我今天也遇到了同样的问题。Office365还需要TLS连接。因此，您应该在代码中添加以下代码

ServicePointManager.Expect100Continue = true;
ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12;

Answer 2

解决。是2FA阻止了它的发生。关闭它，它可以工作