"Unable to read data from the transport connection: net_io_connectionclosed." - Windows Vista Business and SMTP
Asked Answered
H

12

39

Unable to test sending email from .NET code in Windows Vista Business.

I am writing code which I will migrate to an SSIS Package once it its proven. The code is to send an error message via email to a list of recipients.

The code is below, however I am getting an exception when I execute the code.

I created a simple class to do the mailing... the design could be better, I am testing functionality before implementing more robust functionality, methods, etc.

namespace LabDemos
{
    class Program
    {
        static void Main(string[] args)
        {
            Mailer m = new Mailer();
            m.test();    
        }
    }
}

namespace LabDemos
{
    class MyMailer
    {    
        List<string> _to = new List<string>();
        List<string> _cc = new List<string>();
        List<string> _bcc = new List<string>();
        String _msgFrom = "";
        String _msgSubject = "";
        String _msgBody = "";            

        public void test(){
        //create the mail message
        MailMessage mail = new MailMessage();

        //set the addresses
        mail.From = new MailAddress("[email protected]");            

        //set the content
        mail.Subject = "This is an email";
        mail.Body = "this is a sample body";
        mail.IsBodyHtml = false;    

        //send the message
        SmtpClient smtp = new SmtpClient();
        smtp.Host = "emailservername";
        smtp.Port = 25;
        smtp.UseDefaultCredentials = true;
        smtp.Send(mail);            
    }
}

Exception Message

Inner Exception
{"Unable to read data from the transport connection: net_io_connectionclosed."}

Stack Trace
"   at System.Net.Mail.SmtpReplyReaderFactory.ProcessRead(Byte[] buffer, Int32 offset, Int32 read, Boolean readLine)\r\n   at System.Net.Mail.SmtpReplyReaderFactory.ReadLines(SmtpReplyReader caller, Boolean oneLine)\r\n   at System.Net.Mail.SmtpReplyReaderFactory.ReadLine(SmtpReplyReader caller)\r\n   at System.Net.Mail.SmtpConnection.GetConnection(String host, Int32 port)\r\n   at System.Net.Mail.SmtpTransport.GetConnection(String host, Int32 port)\r\n   at System.Net.Mail.SmtpClient.GetConnection()\r\n   at System.Net.Mail.SmtpClient.Send(MailMessage message)"


Outer Exception
  System.Net.Mail.SmtpException was unhandled
  Message="Failure sending mail."
  Source="System"
  StackTrace:
       at System.Net.Mail.SmtpClient.Send(MailMessage message)
       at LabDemos.Mailer.test() in C:\Users\username\Documents\Visual Studio 2008\Projects\LabDemos\LabDemos\Mailer.cs:line 40
       at LabDemos.Program.Main(String[] args) in C:\Users\username\Documents\Visual Studio 2008\Projects\LabDemos\LabDemos\Program.cs:line 48
       at System.AppDomain._nExecuteAssembly(Assembly assembly, String[] args)
       at System.AppDomain.nExecuteAssembly(Assembly assembly, String[] args)
       at System.Runtime.Hosting.ManifestRunner.Run(Boolean checkAptModel)
       at System.Runtime.Hosting.ManifestRunner.ExecuteAsAssembly()
       at System.Runtime.Hosting.ApplicationActivator.CreateInstance(ActivationContext activationContext, String[] activationCustomData)
       at System.Runtime.Hosting.ApplicationActivator.CreateInstance(ActivationContext activationContext)
       at System.Activator.CreateInstance(ActivationContext activationContext)
       at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssemblyDebugInZone()
       at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
       at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
       at System.Threading.ThreadHelper.ThreadStart()
  InnerException: System.IO.IOException
       Message="Unable to read data from the transport connection: net_io_connectionclosed."
       Source="System"
       StackTrace:
            at System.Net.Mail.SmtpReplyReaderFactory.ProcessRead(Byte[] buffer, Int32 offset, Int32 read, Boolean readLine)
            at System.Net.Mail.SmtpReplyReaderFactory.ReadLines(SmtpReplyReader caller, Boolean oneLine)
            at System.Net.Mail.SmtpReplyReaderFactory.ReadLine(SmtpReplyReader caller)
            at System.Net.Mail.SmtpConnection.GetConnection(String host, Int32 port)
            at System.Net.Mail.SmtpTransport.GetConnection(String host, Int32 port)
            at System.Net.Mail.SmtpClient.GetConnection()
            at System.Net.Mail.SmtpClient.Send(MailMessage message)
       InnerException: 
Hepta answered 17/7, 2009 at 15:5 Comment(3)
I'm not going to provide an answer for this one simply because I don't know enough about SMTP to feel good about it. However, this definitely sounds like an environment issue (probably in the IIS settings). Are you using 1) "localhost" for smtp.Host 2) a remote server for smtp.Host and/or 3) a specific IP rather than a hostname?Being
I my mail host is being referred to by name. Example "exchange". I have tested DNS via pinging the server. This was successful. I also tested port access via telnet to port 25. This was also successful. I have tested the code on another machine and was able to send the message. It seems to me I need to install some type of SMTP service/protocol on the machine. The machine on which the code failed is Windows Vista Business. The tests were successful on Windows Server 2008 Standard.Hepta
please refer to: #13689765Bennett
R
16

There are several things that can cause this problem, and here are some of the things that I've found. Questions: You mention "Exchange" -- Is this an exchange server? Does the host require authentication (maybe you need to add authentication to the client)? What I would try doing first is assigning the host to the static IP address instead of the host name to see if that works first. If it does then it's most likely a problem with the DNS mapping.

If you are running your exchange server with Virtualization, you need to configure the SmtpClient to the host IP of the Virtual Server, not the physical hosting server name or IP. Right click on Default SMTP virtual server, select Properties, then go to Access tab, click Relay then add the IP address of the computer that send SMTP request to the SMTP server. (ASP.net site)

If this doesn't work, it's because the server is blocking you from sending SMTP packets. You need to make sure to add the box you are sending the SMTP messages from to the SMTP server. This is done through IIS's authentication tab.

I would also like to point out that you should dispose the mail client, or use the client in a "using" statement. This will make sure that the "QUIT" is sent to the server and gracefully close the connection.

using(SmtpClient smtp = new SmtpClient())
{
    smtp.Host = "emailservername";
    smtp.Port = 25;
    smtp.UseDefaultCredentials = true;
    smtp.Send(mail)
}
Rodolforodolph answered 29/4, 2011 at 12:44 Comment(2)
I am having trouble finding anything that confirms a using statement sends the QUIT when finished. In short how to gracefully close the connection without a using statement.Junji
If you will look at the documentation for SmtpClient.Dispose(), you will see this: "Sends a QUIT message to the SMTP server, gracefully ends the TCP connection, and releases all resources used by the current instance of the System.Net.Mail.SmtpClient class."Spiderwort
S
7

Restart IIS. I know this sounds silly, to do a restart for everything. (and sorry to bump up an old thread). But sometimes restarting IIS works magic. I faced the exact same issue and restarting solved it.

Might have happened cause temporarily the name 'localhost' couldn't be resolved. I;m just posting here so that someone who faces it now will probably try this quick fix before attempting to investigate further. Hope it helps

Sterol answered 28/6, 2012 at 11:37 Comment(0)
H
6

If you've specified an IP address in the SMTP Service settings then make sure you're specifying that IP address of the machine within IIS7 and not putting localhost.

IIS7 makes it easy to select 'localhost' but that will lead to this error if the IP for instance is 10.0.0.1

Humbug answered 11/4, 2010 at 6:52 Comment(0)
H
6

If you are using localhost (Use Localhost) in IIS 7, then change it to IP address of the machine instead of localhost or 127.0.0.1

Also follow below link to update your mail server relay accordingly:

Mailbox unavailable. The server response was: 5.7.1 Unable to relay for [email protected]

Hyperform answered 6/12, 2012 at 17:22 Comment(0)
G
3

Vista and Windows 7 does not have any SMTP server, this facility has been removed since Windows XP, so you need to setup your SMTP server explicitly, several tools are available in market for that, you can check that out. Also once you configure the SMTP, remember to check the server name which you would be using to send the e-mail.

Gametophyte answered 31/1, 2011 at 11:20 Comment(0)
Z
2

I had the same issue since I had multiple IP on my server (Virtual Servers) and my host was pointing to localhost while my SMTP Virtual Server was assigned to one particular IP:

 <smtp deliveryMethod="Network">
       <network host="localhost" port="25" defaultCredentials="false"/>
 </smtp>

There are 2 solutions for this:

  1. Change your code and set host to the particular IP that is being used by SMTP Virtual Server instead of localhost.
  2. Change SMTP Virtual Server IP to All Unassigned

To see/change SMTP Virtual Server IP: Right click on Default SMTP virtual server, select Properties, on General tab change/see IP address.

Hope this saves someone's day with the same issue.

Zebe answered 12/2, 2015 at 0:39 Comment(0)
E
2

I developed a Windows Service application in VB using .NET Framework v4.5 and recently ran into this issue.

First, a little background - I ran into the OP's error after trying to deal with the error "Service not available, closing transmission channel. The server response was: Error: too many messages in one session" which was resolved by calling the Dispose method on the SmtpClient object after each email sent. Just to be ultra safe, I also called Dispose on the MailMessage object.

Okay, so now the 'too many messages in one session' issue is resolved but now I occasionally got the 'Unable to read data from the transport connection: net_io_connectionclosed' error. Awesome. Turns out I had not implemented my email class consistently - in one instance, it was being disposed of while in the other it was not.

Here's an example of what resolved both issues for me (it's in VB but you get the idea):

With New clsEmail(True)
    With .Message
        .To.Add("[email protected]")
        .Subject = msgSubject
        .Body = msgContents
    End With

    .Server.Send(.Message)
    .Server.Dispose()
    .Message.Dispose()
End With

My email class has, among other things, has 2 properties - Message (System.Net.Mail.MailMessage) and Server (System.Net.Mail.SmtpClient) which is what's being disposed in this example.

I haven't had a single problem after hundreds of emails once every single instance that sends email in my service was implemented in this way.

Earplug answered 11/8, 2015 at 19:35 Comment(2)
Creating a new SmtpClient with every message may negatively impact your performance. Instead, I reuse the SmtpClient until the message count gets to something like 6,000 and then I Dispose of it and create a new one. #35573284Frig
Good feedback, Doug. The reason disposing after each email resolved my issue is essentially because it closes the SMTP server connection, thereby ensuring I'm always below the server's message limit per connection. So if you know your SMTP server has a limit of 6k msgs per connection, then it would make sense to keep your SmtpClient object alive for 6k messages before disposing it. Additionally, if you're keeping an SmtpClient alive over a long period of time, you may want to include retry logic in your exception handling for when the connection is unexpectedly closed due to external factors.Earplug
H
1

I have found that the Vista Business OS does not come with IIS SMTP. I suspect this is the missing piece of the puzzle. Has anyone had any luck with this issue?

Hepta answered 28/7, 2009 at 23:31 Comment(0)
E
1

Is your code incompleted.Dash is correct in identifying it.Other then that check smtp component is installed or not check link text

Eggert answered 19/1, 2011 at 11:59 Comment(0)
N
1

I am facing this issue last 6hr and I am new on that so I am trying to solve this issue in following way

1) I opened command prompt (e.g. Ctrl + R type cmd and enter).
2) And check to SMTP server ping and check response.
3) If it’s gets response then it’s ok and to move next step 4 other wise smtp name is wrong.
4) Then I check by telnet smtp port (e.g. 25 ) is open or not.
5) Using this cmd we check the SMTP response.
6) telnet "yoursmtpname" "portno” (e.g. telnet smtp.gmail.com 25)
7) If telnet is not working, please install or add from control panel in add new features.
8) If it’s working then it’s pass result like.
9) 220 mx.google.com ESMTP .

Using above steps we can find out smtp connection is ready or not to sending mail.

Negligent answered 24/7, 2014 at 12:11 Comment(0)
P
1

I was facing the same issue for one month. I tried all the possible solutions provided on Microsoft's official site. Finally, I found the root cause of it. I have updated targetFramework from 4.5.2 to 4.6.1 in web.config file.

compilation debug="true" targetFramework="4.6.1" httpRuntime maxRequestLength="183500800" executionTimeout="3600" targetFramework="4.6.1" enableVersionHeader="false"

the above solution worked for me, and now my emails are triggering successfully from the application.

Phono answered 18/2, 2022 at 11:47 Comment(0)
B
0

upgrade to .NET 4.0 and apply all security updates

Boehmite answered 29/4, 2011 at 6:20 Comment(0)

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