c#之在 C# .net 中发送邮件失败

我发送电子邮件的代码在 psat 两周内正常工作。但是现在它显示了类似

Failure Sending Mail.

我不知道为什么会出现这个问题。上周放了一些新的防火墙策略，是不是因为这个问题才出现？我该怎么办？

这是我的代码:

 protected void Button1_Click(object sender, EventArgs e) 
    { 
        try 
        { 
            if (TextBox1.Text == "") 
            { 
 
                string alertmessage = ""; 
                alertmessage = "Email ID. cannot be blank "; 
                this.CreateMessageAlert(this, alertmessage, "alertKey"); 
                TextBox1.Focus(); 
            } 
            else if (TextBox2.Text == "") 
            { 
 
                string alertmessage = ""; 
                alertmessage = "CC To cannot be blank "; 
                this.CreateMessageAlert(this, alertmessage, "alertKey"); 
                TextBox2.Focus(); 
            } 
            else if (TextBox3.Text == "") 
            { 
 
                string alertmessage = ""; 
                alertmessage = "Subject cannot be blank "; 
                this.CreateMessageAlert(this, alertmessage, "alertKey"); 
                TextBox3.Focus(); 
            } 
            else if (TextBox4.Text == "") 
            { 
 
                string alertmessage = ""; 
                alertmessage = "Message Body cannot be blank "; 
                this.CreateMessageAlert(this, alertmessage, "alertKey"); 
                TextBox4.Focus(); 
            } 
            //else if (upSignature.FileName == "") 
            //{ 
            //    ctr = 1; 
            //    string alertmessage = ""; 
            //    alertmessage = "Attachment  Missing..."; 
            //    this.CreateMessageAlert(this, alertmessage, "alertKey"); 
            //    upSignature.Focus(); 
            //} 
 
            else 
            { 
 
 
                string photo = "Enquiry" + Session["MRNO"].ToString() + FileUpload1.FileName; 
                string strpath = Request.MapPath("~/"); 
                FileUpload1.SaveAs(strpath + "/Enquiry/" + photo); 
 
 
                try 
                { 
                    MailMessage mail = new MailMessage(); 
                    mail.To.Add(new MailAddress(TextBox1.Text.Trim())); 
                    mail.From = new MailAddress("XXXXXXX"); 
                    mail.Subject = "Enquiry for MRNO " + " " + " " + Session["MRNO"].ToString() + " " + " " + "Reg."; 
                    mail.CC.Add(TextBox2.Text.Trim()); 
                    mail.Body = TextBox4.Text.Trim(); 
 
                        mail.Attachments.Add(new Attachment(FileUpload1.PostedFile.InputStream, FileUpload1.FileName)); 
                        mail.Attachments.Add(new Attachment(FileUpload2.PostedFile.InputStream, FileUpload2.FileName)); 
 
                    //Attachment attach = new Attachment(strpath + "/Enquiry/" + photo); 
                    //mail.Attachments.Add(attach); 
 
 
                    SmtpClient smtp = new SmtpClient("smtp.gmail.com", 587); 
 
                    smtp.EnableSsl = true; 
 
                    smtp.UseDefaultCredentials = false; 
                    smtp.Credentials = new NetworkCredential("XXXXXX", "XXXXXXX"); 
 
                    smtp.Send(mail); 
 
                    string alertmessage = ""; 
                    alertmessage = "Mail Has Been Sent"; 
                    this.CreateMessageAlert(this, alertmessage, "alertKey"); 
 
 
                    //   Page.RegisterStartupScript("close", "<script language=javascript>self.close();</script>"); 
 
                } 
                catch (Exception ex) 
                { 
                    Response.Write(ex.Message); 
                } 
            } 
        } 
        catch (Exception ex1) 
        { 
            Response.Write(ex1.Message); 
        } 
 
    } 

请您参考如下方法:

发送邮件需要开启587端口。就此与您的网络团队核实并确保它已打开