Email using System.Net.Mail through Google Apps Timing out - asp.net

Question

I have a ASP.NET 4.0 web application, which the HR team uses to send out surveys to employees. Since we use a Google Apps, I am trying to send these survey emails through the Google Apps Account.
I have used the following settings to send out emails.
Host - smtp.gmail.com
Port - 587
EnableSsl=true
along with my username and password.
This is the code for sending out emails.
using (SmtpClient smtp = new SmtpClient())
{
smtp.Timeout = 0;
smtp.Send(message);
}
The settings are in the web.config and are read from there.
Now my issue..
The hr team selects multiple users to send the survey to. They could just select 1 or maybe up to 100 at a time to send out surveys. Since each survey link has to be different, I iterate the list of users and email them.
Now after the application send out a maximum of 12 emails, it stops sending out any more. The next email it tries to send it throws an error.
Message = The operation has timed out.
Status Code =GeneralFailure
Stack Trace = at System.Net.Mail.SmtpClient.Send(MailMessage message)
at ABC.Business.Mail.SendMail(MailMessage message, String& errorMessage)
Then onwards if I retry again it throws an error
Message = Failure sending mail.
Status Code =GeneralFailure
Stack Trace = at System.Net.Mail.SmtpClient.Send(MailMessage message)
at ABC.Business.Mail.SendMail(MailMessage message, String& errorMessage)
If its come to this state, the only way out is to retart IIS. If I restart IIS, it starts working fine again for the next 12 odd.
What could be the issue? Please help.

Answer 1

You shouldn't set the Timeout to zero.
Its default is 100,000mS (100 seconds), try to leave it at that at least.

Answer 2

System.Net.Mail only supports "Explicit SSL".
Explicit SSL
System.Net.Mail only supports "Explicit SSL". Explicit SSL starts as unencrypted on port 25, then issues a STARTDLS and switches to an Encrypted connection. See RFC 2228.
Explicit SLL would go something like: Connect on 25 -> StartTLS (starts to encrypt) -> authenticate -> send data
If the SMTP server expects SSL/TLS connection right from the start then this will not work.
Implicit SSL
There is no way to use Implicit SSL (SMTPS) with System.Net.Mail. Implicit SSL would have the entire connection is wrapped in an SSL layer. A specific port would be used (port 465 is common). There is no formal RFC covering Implicit SSL.
Implicit SLL would go something like: Start SSL (start encryption) -> Connect -> Authenticate -> send data
This is not considered a bug, it’s a feature request. There are two types of SSL authentication for SMTP, and we only support one (by design) – Explicit SSL.
Demo Code:
*
protected void Btn_SendMail_Click(object sender, EventArgs e)
{
try
{
var fromAddress = "xyz#gmail.com";
var toAddress = "abc#gmail.com";
const string fromPassword = "xxxxxxxx";
string subject = "Sending Demonstration";
string body = "From: " + txtFrom.Text + "\n";
var smtp = new System.Net.Mail.SmtpClient();
{
smtp.Host = "smtp.gmail.com";
smtp.Port = 25;
smtp.EnableSsl = true;
smtp.Credentials = new NetworkCredential(fromAddress, fromPassword);
}
smtp.Send(fromAddress, toAddress, subject, body);
Response.Write("<script language=javascript> alert('send')</script>");
}
catch (Exception ex)
{
txtBody.Text = ex.Message;
}
}
*
This Code Is Working Without Any Error!!!!

Answer 3

Chris, TimeOut makes ASP.NET application to wait for the request to perform before it shutting down automatically. So, If you give timeOut as zero, ASP.NET will not wait for the request to perform and it will throw error as operation has timed out.
TimeOut should be atleast 180 seconds.
Thanks.