申请关闭之前不会发送电子邮件

Question

我有一个使用 SmtpClient 发送电子邮件的应用程序，但直到应用程序关闭后才会发送电子邮件。我一直在寻找解决问题的方法，但我找不到。

系统确实安装了赛门铁克防病毒软件，这可能是问题所在。

有人有解决这个问题的办法吗？

这是我正在使用的代码。

public class EMail
{
    private string server;
    public string Server {get{return this.server;}set{this.server = value;}}
    private string to;
    public string To {get{return this.to;}set{this.to = value;}}
    private string from;
    public string From {get{return this.from;}set{this.from = value;}}
    private string subject;
    public string Subject {get{return this.subject;}set{this.subject = value;}}
    private string body;
    public string Body {get{return this.body;}set{this.body = value;}}

    public EMail()
    {}
    public EMail(string _server, string _to, string _from, string _subject, string _body)
    {
        this.Server = _server;
        this.To = _to;
        this.From = _from;
        this.Subject = _subject;
        this.Body = _body;
    }   

    public void Send()
    {
        using(System.Net.Mail.MailMessage message = new System.Net.Mail.MailMessage(this.From, this.To, this.Subject, this.Body))
        {        
            message.IsBodyHtml = true;
            System.Net.Mail.SmtpClient client = new System.Net.Mail.SmtpClient(this.Server);
            client.DeliveryMethod = System.Net.Mail.SmtpDeliveryMethod.Network;
            //I have tried this, but it still does not work.
            //client.ServicePoint.ConnectionLeaseTimeout = 0;
            try 
            {
                client.Send(message);
            }  
            catch(System.Exception ex) 
            {
                System.Windows.Forms.MessageBox.Show(ex.ToString());              
            }
        }
    }
}

编辑：

事实证明，电子邮件最终在 2-3 分钟后发送。看起来好像正在由交换服务器排队，或者 SmtpClient 连接最终超时并被服务器关闭。

编辑：

我已经尝试过。

client.ServicePoint.ConnectionLeaseTimeout = 1;
client.ServicePoint.MaxIdleTime = 1;

Answer 1

我终于；在 StackOverflow 和其他各种研究来源的帮助下，我们找到了解决方案。通过设置 System.Net.ServicePointManager.MaxServicePointIdleTime = 1，邮件将立即发送。

这是最终的代码。

public class EMail
{
    private string server;
    public string Server {get{return this.server;}set{this.server = value;}}
    private string to;
    public string To {get{return this.to;}set{this.to = value;}}
    private string from;
    public string From {get{return this.from;}set{this.from = value;}}
    private string subject;
    public string Subject {get{return this.subject;}set{this.subject = value;}}
    private string body;
    public string Body {get{return this.body;}set{this.body = value;}}

    public EMail()
    {}
    public EMail(string _server, string _to, string _from, string _subject, string _body)
    {
        this.Server = _server;
        this.To = _to;
        this.From = _from;
        this.Subject = _subject;
        this.Body = _body;
    }   

    public void Send()
    {
        using(System.Net.Mail.MailMessage message = new System.Net.Mail.MailMessage(this.From, this.To, this.Subject, this.Body))
        {        
            message.IsBodyHtml = true;
            System.Net.Mail.SmtpClient client = new System.Net.Mail.SmtpClient(this.Server);
            client.DeliveryMethod = System.Net.Mail.SmtpDeliveryMethod.Network;

            int temp = System.Net.ServicePointManager.MaxServicePointIdleTime; //<- Store the original value.
            System.Net.ServicePointManager.MaxServicePointIdleTime = 1; //<- Change the idle time to 1.

            try 
            {
                client.Send(message);
            }  
            catch(System.Exception ex) 
            {
                System.Windows.Forms.MessageBox.Show(ex.ToString());              
            }
            finally
            {
                System.Net.ServicePointManager.MaxServicePointIdleTime = temp; //<- Set the idle time back to what it was.
            }
        }
    }
}

谢谢大家的帮助！特别是冰曼尼德。

Answer 2

可能的原因是连接保持打开状态。尝试在 Send 方法末尾关闭连接，看看是否有效。

编辑：现在 SmtpClient 实现了 IDispose，这似乎是 .NET 4.0 中的情况。

Answer 3

我打赌您已经安装了诺顿防病毒软件。这似乎是诺顿防病毒软件的一个已知问题。您可以通过打开诺顿防病毒软件并禁用电子邮件工具来解决此问题。让我知道这是否适合您。

Answer 4

好的测试人员...如果您想解决诺顿问题，这非常简单。添加以下行：

message.EnableSsl = true;

这将导致 smtp 客户端加密您的连接，从而将其发送到诺顿监控的不同端口上。看看是否有效！

Answer 5

另外，对于 System.Net.Mail.MailMessage 等任何一次性类型，您应该使用“using”块：

public void Send() 
{ 
    using (System.Net.Mail.MailMessage message = new System.Net.Mail.MailMessage(this.From, this.To, this.Subject, this.Body))
    {
        message.IsBodyHtml = true; 
        System.Net.Mail.SmtpClient client = new System.Net.Mail.SmtpClient(this.Server); 
        client.DeliveryMethod = System.Net.Mail.SmtpDeliveryMethod.Network; 
        try  
        { 
            client.Send(message); 
        }   
        catch(System.Exception ex)  
        { 
            System.Windows.Forms.MessageBox.Show(ex.ToString());               
        }
    } 
} 

Answer 6

System.Net.Mail.MailMessage 和 System.Net.Mail.SmtpClient 都实现了 IDisposable，这意味着您需要调用 完成后将其丢弃。 IE：

using (System.Net.Mail.MailMessage message = new System.Net.Mail.MailMessage(this.From, this.To, this.Subject, this.Body))
{
    message.IsBodyHtml = true; 
    using(System.Net.Mail.SmtpClient client = new System.Net.Mail.SmtpClient(this.Server))
    {
        client.DeliveryMethod = System.Net.Mail.SmtpDeliveryMethod.Network; 
        try  
        { 
            client.Send(message); 
        }   
        catch(System.Exception ex)  
        { 
            System.Windows.Forms.MessageBox.Show(ex.ToString());               
        }
    }
}