@Andres Pompiglio:是的，你必须至少修改一次密码。 这个代码工作得很好:

//Satrt Send Email Function
public string SendMail(string toList, string from, string ccList,
    string subject, string body)
{

    MailMessage message = new MailMessage();
    SmtpClient smtpClient = new SmtpClient();
    string msg = string.Empty;
    try
    {
        MailAddress fromAddress = new MailAddress(from);
        message.From = fromAddress;
        message.To.Add(toList);
        if (ccList != null && ccList != string.Empty)
            message.CC.Add(ccList);
        message.Subject = subject;
        message.IsBodyHtml = true;
        message.Body = body;
        // We use gmail as our smtp client
        smtpClient.Host = "smtp.gmail.com";   
        smtpClient.Port = 587;
        smtpClient.EnableSsl = true;
        smtpClient.UseDefaultCredentials = true;
        smtpClient.Credentials = new System.Net.NetworkCredential(
            "Your Gmail User Name", "Your Gmail Password");

        smtpClient.Send(message);
        msg = "Successful<BR>";
    }
    catch (Exception ex)
    {
        msg = ex.Message;
    }
    return msg;
}
//End Send Email Function

并且你可以使用以下方法调用函数:

Response.Write(SendMail(recipient Address, "UserName@gmail.com", "ccList if any", "subject", "body"))

我从我的gmail帐户发送电子邮件也遇到了一些问题，这是由于上述几种情况。 以下是我如何让它工作的总结，同时保持它的灵活性:

首先，建立你的GMail账户: 启用IMAP并断言正确的最大消息数(可以在这里执行) 确保你的密码至少有7个字符，并且是强密码(根据谷歌) 确保你不需要先输入验证码。您可以通过从浏览器发送测试电子邮件来做到这一点。 在web中进行更改。config(或app.config，我还没有尝试过，但我认为它也很容易让它在windows应用程序中工作):

<configuration>
    <appSettings>
        <add key="EnableSSLOnMail" value="True"/>   
    </appSettings>

    <!-- other settings --> 

    ...

    <!-- system.net settings -->
    <system.net>
        <mailSettings>
            <smtp from="yourusername@gmail.com" deliveryMethod="Network">
                <network 
                    defaultCredentials="false" 
                    host="smtp.gmail.com" 
                    port="587" 
                    password="stR0ngPassW0rd" 
                    userName="yourusername@gmail.com"
                    />
                <!-- When using .Net 4.0 (or later) add attribute: enableSsl="true" and you're all set-->
            </smtp>
        </mailSettings>
    </system.net>
</configuration>

Add a Class to your project:

Imports System.Net.Mail

Public Class SSLMail

    Public Shared Sub SendMail(ByVal e As System.Web.UI.WebControls.MailMessageEventArgs)

        GetSmtpClient.Send(e.Message)

        'Since the message is sent here, set cancel=true so the original SmtpClient will not try to send the message too:
        e.Cancel = True

    End Sub

    Public Shared Sub SendMail(ByVal Msg As MailMessage)
        GetSmtpClient.Send(Msg)
    End Sub

    Public Shared Function GetSmtpClient() As SmtpClient

        Dim smtp As New Net.Mail.SmtpClient
        'Read EnableSSL setting from web.config
        smtp.EnableSsl = CBool(ConfigurationManager.AppSettings("EnableSSLOnMail"))
        Return smtp
    End Function

End Class

现在，无论何时想要发送电子邮件，都需要调用SSLMail。发送邮件:

例如，在带有PasswordRecovery控件的Page中:

Partial Class RecoverPassword
Inherits System.Web.UI.Page

Protected Sub RecoverPwd_SendingMail(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.MailMessageEventArgs) Handles RecoverPwd.SendingMail
    e.Message.Bcc.Add("webmaster@example.com")
    SSLMail.SendMail(e)
End Sub

End Class

或者在代码的任何地方都可以调用:

SSLMail.SendMail(New system.Net.Mail.MailMessage("from@from.com","to@to.com", "Subject", "Body"})

我希望这能帮助任何遇到这篇文章的人!(我用的是VB。NET，但是我认为把它转换成任何。NET语言都很简单。)

Dim SMTPClientObj As New Net.Mail.SmtpClient
SMTPClientObj.UseDefaultCredentials = False
SMTPClientObj.Credentials = New System.Net.NetworkCredential("myusername@gmail.com", "mypwd")
SMTPClientObj.Host = "smtp.gmail.com"
SMTPClientObj.Port = 587
SMTPClientObj.EnableSsl = True
SMTPClientObj.Send("myusername@gmail.com","yourusername@gmail.com","test","testbody")

如果您得到诸如“SMTP服务器需要安全连接或客户端未经过身份验证。服务器的响应是:5.5.1需要身份验证。要了解更多信息，请访问“在此之前，确保行SMTPClientObj。UseDefaultCredentials = False，这一行应该在smtpclientb . credentials之前。

我确实尝试将这两行反向切换，并返回5.5.1 Authentication Required错误。

我不确定这需要哪个.NET版本，因为eglasius提到没有匹配的enableSsl设置(我使用。net 4.0，但我怀疑它可以在。net 2.0或更高版本中工作)，但这个配置只是为我工作(并且不需要您使用任何编程配置):

<system.net>
  <mailSettings>
    <smtp from="myusername@gmail.com" deliveryMethod="Network">
      <network defaultCredentials="false" enableSsl="true" host="smtp.gmail.com" port="587" password="password" userName="myusername@gmail.com"/>
    </smtp>
  </mailSettings>
</system.net>

您可能需要先在Gmail帐户上启用POP或IMAP: https://mail.google.com/mail/?shva=1#settings/fwdandpop

我建议先用普通的邮件客户端尝试一下…

我也尝试了许多解决方案，但做一些改变，它会起作用

host = smtp.gmail.com
port = 587
username = email@gmail.com
password = password
enabledssl = true

与smtpclient上述参数工作在gmail

You can also connect via port 465, but due to some limitations of the System.Net.Mail namespace you may have to alter your code. This is because the namespace does not offer the ability to make implicit SSL connections. This is discussed at http://blogs.msdn.com/b/webdav_101/archive/2008/06/02/system-net-mail-with-ssl-to-authenticate-against-port-465.aspx, and I have supplied an example of how to use the CDO (Collaborative Data Object) in another discussion (GMail SMTP via C# .Net errors on all ports).