You can alter web.config like this so
that when you send email it will
instead be created as an .EML file in
c:\LocalDir.

<configuration>  
     <system.net>    
      <mailSettings>      
       <smtp deliveryMethod="SpecifiedPickupDirectory">        
        <specifiedPickupDirectory pickupDirectoryLocation="c:\LocalDir"/>      
       </smtp>    
      </mailSettings>  
     </system.net>
    </configuration>

如果您不想/不能更改web.config,也可以使用相同的设置创建SmtpClient类的实例.在C#中看起来像这样：

var smtpClient = new SmtpClient();
smtpClient.DeliveryMethod = SmtpDeliveryMethod.SpecifiedPickupDirectory;
var emailPickupDirectory = HostingEnvironment.MapPath("~/EmailPickup");
if (!Directory.Exists(emailPickupDirectory)) { 
    Directory.CreateDirectory(emailPickupDirectory)
}
smtpClient.PickupDirectoryLocation = emailPickupDirectory;