我已经使用以下设置配置了我的Web.Config文件：
<system.net> <mailSettings> <smtp deliveryMethod="Network"> <network enableSsl="true" defaultCredentials="false" host="smtp.gmail.com" port="587" userName="xxMyUserNamexx@gmail.com" password="xxMyPasswordxx" /> </smtp> </mailSettings> </system.net>
public void SendMail(string fromDisplayName,string fromEmailAddress,string toEmailAddress,string subject,string body)
{
MailAddress from = new MailAddress(fromEmailAddress,fromDisplayName);
MailAddress to = new MailAddress(toEmailAddress);
MailMessage mailMessage = new MailMessage(from,to);
mailMessage.Body = body;
mailMessage.Subject = subject;
SmtpClient client = new SmtpClient();
//client.UseDefaultCredentials = false;
client.Send(mailMessage);
}
以上代码按预期工作正常.有什么困扰我的是注释行client.UseDefaultCredentials = false; – 如果我要取消对该行的注释,我将收到一条异常消息,其中指出：
The SMTP server requires a secure connection or the client was not
authenticated. The server response was: 5.5.1 Authentication required.
更重要的是,如果我将UseDefaultCredentials属性设置为true或false,我仍然会收到异常消息.避免异常消息的唯一方法是完全删除该行.
这个行为是否正常？你能解释为什么我收到异常消息吗？
解决方法
So why would me explicitly setting the property to false throw an exception?
原因是因为UseDefaultCredentials的setter将Credentials属性设置为null,如果将其设置为false,或者将其设置为CredentialCache.DefaultNetworkCredentials属性(如果设置为true). DefaultNetworkCredentials属性为defined by MSDN as：
The credentials returned by DefaultNetworkCredentials represents the authentication credentials for the current security context in which the application is running. For a client-side application,these are usually the Windows credentials (user name,password,and domain) of the user running the application. For ASP.NET applications,the default network credentials are the user credentials of the logged-in user,or the user being impersonated.
当您将UseDefaultCredentials设置为true时,它将使用您的IIS用户,并且假设您的IIS用户与您使用的任何SMTP服务器的帐户不具有与您的帐户相同的身份验证凭据.将UseDefaultCredentials设置为false将设置的凭据设置为false.所以无论哪种方式你都会得到这个错误.
以下是使用dotPeek的UseDefaultCredentials设置器：
set
{
if (this.InCall)
{
throw new InvalidOperationException(
SR.GetString("SmtpInvalidOperationDuringSend"));
}
this.transport.Credentials = value
? (ICredentialsByHost) CredentialCache.DefaultNetworkCredentials
: (ICredentialsByHost) null;
}
