I have an ASP.NET 2.0 Web Application.  I am trying to send an email to
myself from Global.asax in the Application_Error event handler.  I have been
able to successfully send emails from the rest of the application using the
exact same logic.  For some reason, it does not work in global.asax.  I get a
"Failure Sending Mail" error message with a more detailed explanation of
"Unable to read data from the transport connection: An existing connection
was forcibly closed by the remote host.".  This is in a hosted environment,
and it IS working for other pages in the app (making me think I need to do
something different in the Application_Error function.

I am using the System.Net.Mail class.  Below is my code and the detailed
error (notice I have some general information stored in web.config which is
pasted below as well):

GLOBAL.ASAX
--------------------------------------------------------
void Application_Error(object sender, EventArgs e)
   {
       // Code that runs when an unhandled error occurs
       Exception ex = Server.GetLastError();
    string strEmailAddressTo = "myemail@test.com";
       string strEmailAddressFrom = "myemail@test.com";
           

       string ErrorMessage = ex.Message +
           "\nSOURCE: " + ex.Source +
           "\nFORM: " + Request.Form.ToString() +
               "\nQUERYSTRING: " +
               Request.QueryString.ToString() +
               "\nTARGETSITE: " + ex.TargetSite +
              "\nSTACKTRACE: " + ex.StackTrace;

        //1) Create the mail message instance
       MailMessage mm = new MailMessage(strEmailAddressFrom,
strEmailAddressTo);

       //2) Assign the Mail Message's Properties
       // Subject        
       mm.Subject = "ERROR OCCURRED";

       //3) Body
       mm.Body = ErrorMessage.ToString();
       mm.IsBodyHtml = false;

       //4) Create the SMTP Client Object
       SmtpClient smtp = new SmtpClient();

       
       //5) Send the mail message (will use the web.config settings)
       smtp.Send(mm);
}

web.config
------------------------------------------------------------
<system.net>
   <mailSettings>
     <smtp>
       <network host="[mynetworkHost]" port="25" />
     </smtp>
   </mailSettings>
 </system.net>

DETAILED ERROR MESSAGE:
-------------------------------------------------------------
<ExceptionInformation><AdditionalInformationProperty
ExceptionManager.MachineName="XXXXX" ExceptionManager.TimeStamp="10/2/2007
1:32:25 AM"
ExceptionManager.FullName="Microsoft.ApplicationBlocks.ExceptionManagement,
Version=1.0.2830.35366, Culture=neutral, PublicKeyToken=null"
ExceptionManager.AppDomainName="/LM/w3svc/814863/root-11-128357766911129800"
ExceptionManager.ThreadIdentity="" ExceptionManager.WindowsIdentity="NT
AUTHORITY\NETWORK SERVICE" /><Exception
ExceptionType="System.Net.Mail.SmtpException" StatusCode="GeneralFailure"
Message="Failure sending mail."
Data="System.Collections.ListDictionaryInternal" TargetSite="Void
Send(System.Net.Mail.MailMessage)" Source="System"><StackTrace>   at
System.Net.Mail.SmtpClient.Send(MailMessage message)
  in  \\[webpath]\web\Global.asax:line 101</StackTrace><Exception
ExceptionType="System.IO.IOException" Message="Unable to read data from the
transport connection: An existing connection was forcibly closed by the
remote host." Data="System.Collections.ListDictionaryInternal"
TargetSite="Int32 Read(Byte[], Int32, Int32)" Source="System"><StackTrace>  
at System.Net.Sockets.NetworkStream.Read(Byte[] buffer, Int32 offset, Int32
size)
  at System.Net.DelegatedStream.Read(Byte[] buffer, Int32 offset, Int32
count)
  at System.Net.BufferedReadStream.Read(Byte[] buffer, Int32 offset, Int32
count)
  at System.Net.Mail.SmtpReplyReaderFactory.ReadLines(SmtpReplyReader
caller, Boolean oneLine)
  at System.Net.Mail.SmtpReplyReaderFactory.ReadLine(SmtpReplyReader caller)
  at System.Net.Mail.SmtpReplyReader.ReadLine()
  at System.Net.Mail.CheckCommand.Send(SmtpConnection conn, String& response)
  at System.Net.Mail.DataStopCommand.Send(SmtpConnection conn)
  at System.Net.Mail.SmtpConnection.OnClose(Object sender, EventArgs args)
  at System.Net.ClosableStream.Close()
  at System.Net.Mail.MailWriter.Close()
  at System.Net.Mail.SmtpClient.Send(MailMessage
message)</StackTrace><Exception
ExceptionType="System.Net.Sockets.SocketException" ErrorCode="10054"
SocketErrorCode="ConnectionReset" NativeErrorCode="10054" Message="An
existing connection was forcibly closed by the remote host"
Data="System.Collections.ListDictionaryInternal" TargetSite="Int32
Receive(Byte[], Int32, Int32, System.Net.Sockets.SocketFlags)"
Source="System"><StackTrace>   at System.Net.Sockets.Socket.Receive(Byte[]
buffer, Int32 offset, Int32 size, SocketFlags socketFlags)
  at System.Net.Sockets.NetworkStream.Read(Byte[] buffer, Int32 offset,
Int32
size)</StackTrace></Exception></Exception></Exception></ExceptionInformation>