IIS session timeout occurs randomly - due to error in sending email - asp.net-mvc

Question

So let me explain the situation. Our asp.net mvc application is running on Windows server 2012 r2 and IIS 8.5.9600.16384. Now randomly user session is lost 4/5 times a day although timeout is set to 1000 minutes in process mode. Now checking the event viewer I found 4 errors occurs when when user session is lost (every time below errors repeat when session is lost). Below are the errors...
1.
An unhandled exception occurred and the process was terminated.
Application ID: /LM/W3SVC/7/ROOT
Process ID: 7680
Exception: System.Net.Mail.SmtpException
Message: The operation has timed out.
StackTrace: at System.Net.Mail.SmtpClient.Send(MailMessage message)
at PDSO.Models.MailClient.<>c__DisplayClass2_1.<SendGMail>b__0(Object o) in
D:\Development\Projects\YunuscoMRP\YunuscoMRP\Models\Repository\MailClient.cs:line 67
at System.Threading.QueueUserWorkItemCallback.WaitCallback_Context(Object state)
at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext,
ContextCallback callback, Object state, Boolean preserveSyncCtx)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback
callback, Object state, Boolean preserveSyncCtx)
at
System.Threading.QueueUserWorkItemCallback.System.Threading.
IThreadPoolWorkItem.ExecuteWorkItem()
at System.Threading.ThreadPoolWorkQueue.Dispatch()
at System.Threading._ThreadPoolWaitCallback.PerformWaitCallback()
`
Application: w3wp.exe
Framework Version: v4.0.30319
Description: The process was terminated due to an unhandled exception.
Exception Info: System.Net.Mail.SmtpException
at System.Net.Mail.SmtpClient.Send(System.Net.Mail.MailMessage)
at PDSO.Models.MailClient+<>c__DisplayClass2_1.<SendGMail>b__0(System.Object)
at System.Threading.QueueUserWorkItemCallback.WaitCallback_Context(System.Object)
at System.Threading.ExecutionContext.RunInternal(System.Threading.ExecutionContext, System.Threading.ContextCallback, System.Object, Boolean)
at System.Threading.ExecutionContext.Run(System.Threading.ExecutionContext, System.Threading.ContextCallback, System.Object, Boolean)
at System.Threading.QueueUserWorkItemCallback.System.Threading.IThreadPoolWorkItem.ExecuteWorkItem()
at System.Threading.ThreadPoolWorkQueue.Dispatch()
at System.Threading._ThreadPoolWaitCallback.PerformWaitCallback()
`
3.
`
Faulting application name: w3wp.exe, version: 8.5.9600.16384, time stamp: 0x52157ba0
Faulting module name: KERNELBASE.dll, version: 6.3.9600.19724, time stamp: 0x5ec50c3e
Exception code: 0xe0434352
Fault offset: 0x000156e8
Faulting process id: 0x1e00
Faulting application start time: 0x01d8165b6e64aacc
Faulting application path: C:\Windows\SysWOW64\inetsrv\w3wp.exe
Faulting module path: C:\Windows\SYSTEM32\KERNELBASE.dll
Report Id: 38d3cbc4-824f-11ec-8116-000c293f4b2c
Faulting package full name:
Faulting package-relative application ID:
`
4.
An unhandled Microsoft .NET Framework exception occurred in w3wp.exe [7680].
Just-In-Time debugging this exception failed with the following error: Debugger could not be
started because no user is logged on.
Check the documentation index for 'Just-in-time debugging, errors' for more information.
I have one class to handle outgoing email. Code is provided below
public string SendGMail(string fromEmail, string toEmail, string mailSubject, string mailBody,
string senderName, string senderPass, string attacmmentLocationPath)
{
try
{
MailMessage mail = new MailMessage();
mail.From = new MailAddress(fromEmail);
mail.To.Add(toEmail);
mail.Subject = mailSubject;
mail.Body = mailBody;
mail.IsBodyHtml = true;
//// mail.Attachments.Add(new Attachment(#attacmmentLocationPath));
//---------------- Enable the block before publish ----------
ThreadPool.QueueUserWorkItem(o =>
{
using (SmtpClient client = new SmtpClient("smtp.office365.com"))
{
client.Port = 587;
client.Credentials = new System.Net.NetworkCredential(senderName, senderPass);
client.EnableSsl = true;
client.Send(mail);
}
});
//-------------------------------------------------------------
return "Success";
}
catch (Exception ex)
{
bool error = new ErrorLogRepository().InsertErrorToDatabase("", "MailClient", "SendGmail", ex.ToString());
return "Error";
}
}
Can anyone suggest what is wrong with my sending email code or what is causing the session timeout/iis restart/application pool restart ?

Answer 1

You should add a try-catch block to your work item to handle the SMTP client exception and log the error gracefully. Because the work item executes outside of your SendMail function, the try-catch block in the SendMail function does not handle the exception.
ThreadPool.QueueUserWorkItem(o =>
{
try
{
using (SmtpClient client = new SmtpClient("smtp.office365.com"))
{
client.Port = 587;
client.Credentials = new System.Net.NetworkCredential(senderName, senderPass);
client.EnableSsl = true;
client.Send(mail);
}
}
catch (Exception ex)
{
bool error = new ErrorLogRepository().InsertErrorToDatabase("", "MailClient", "SendGmail", ex.ToString());
}
});