POP3, C# and Response from Command?


I have an interesting dilemma that started a little while ago.

I have an exchange mailbox that I will access with OWA from a browser.

However, I have an application that will access the mailbox as well and perform most of the activity. That is where the strangeness is happening. Generally, there will be like 600 emails a day that will go into the Inbox and the application will process. As part of the process it will retrieve the necessary message and process it then issue the command to delete the message (DELE {Whatever the number of the message}). Again, for the large majority of the time it processes just fine. Yet, I will randomly get a message in it that just causes havoc. When that message in as in the Inbox more "normal" messages will come in BUT it will never delete those message. As a result, the inbox will build and build.

Here is a little snippet of the code:

try {
        pop3Stream.Write(commandBytes, 0, commandBytes.Length);
        if (isDebug) {
          throw new IOException("Test", new SocketException(10053));
      } catch (IOException ex) {
        //Unable to write data to the transport connection. Check if reconnection should be tried
        isSupressThrow = {execute reconnect};
        if (!isSupressThrow) {

      //read response from server
      response = null;
      try {
        response = pop3StreamReader.ReadLine();
      }catch (IOException ex) {
        //Unable to write data to the transport connection. Check if reconnection should be tried
        isSupressThrow = {execute reconnect}
        if (isSupressThrow) {
          //wait for response one more time
          response = pop3StreamReader.ReadLine();
        } else {
      if (response==null) {
        throw new Pop3Exception("Server "+ popServer + " has not responded, timeout has occured.");

Open in new window

Now, the problem is in that situation with the email that doesn't delete is that the

Open in new window

is "" there is would "normally" get like an "+OK".  All subsequent emails that hit this code get some other cryptic type message that doesn't look like a response from a command.

I need to take that one email that is causing everything out of the mailbox by moving it and only then will everything go back to processing normally.

Any ideas on this? Should I loop on the
response = pop3StreamReader.ReadLine();

Open in new window

line while the response is "" for a certain period of time?

Any thoughts or suggestions on this?

Any information would be greatly appreciated.
Who is Participating?
I wear a lot of hats...

"The solutions and answers provided on Experts Exchange have been extremely helpful to me over the last few years. I wear a lot of hats - Developer, Database Administrator, Help Desk, etc., so I know a lot of things but not a lot about one thing. Experts Exchange gives me answers from people who do know a lot about one thing, in a easy to use platform." -Todd S.

Robberbaron (robr)Commented:
not a POP expert, but there is also an Exchange WebServices API that works directly and well for me.
davismAuthor Commented:
I cannot change the code or anything nor does it make any since. Especially when this has been running fine for almost 2 years.

Any other thoughts or ideas related to this?
ste5anSenior DeveloperCommented:
Just it was running for two years, doesn't mean that it was okay.

But I would assume that the problem may be your pop3Stream. How is it implemented?
C++ 11 Fundamentals

This course will introduce you to C++ 11 and teach you about syntax fundamentals.

davismAuthor Commented:
I will have to provide the info when I get connect to my work again. Once I do I will post the response to your question.

But help me understand, if it's been running fine and has processed over 100,000 emails with no problem but now all of a sudden starts (began on 9/11 actually) and is randomly  encountering an issue how would that constitute not being ok? The machine hasn't been patched so nothing has changed; it has been rebooted on normal quarterly schedules.

I know we have another test environment with a mailbox specific to test. It runs the same program just from a different machine accessing the same mailbox server. I have forwarded the culprit email to that test mailbox and the test server application (which is the same code) deleted it without a problem. But I would imagine the forwarding changed the header and all. How can I get that same email in a different mailbox? That way I could test more to try and isolate the problem with that email or emails like that.
ste5anSenior DeveloperCommented:
The behaviour you've described sounds like the pop3stream is not capturing the Ok from the server. This can be a race condition. This maybe for example by a different bandwidth. My first approach would using a network sniffer to check whether the ok is sent and the timing looks like.

Experts Exchange Solution brought to you by

Your issues matter to us.

Facing a tech roadblock? Get the help and guidance you need from experienced professionals who care. Ask your question anytime, anywhere, with no hassle.

Start your 7-day free trial
davismAuthor Commented:
The result was that it had to be attempted again. The first read didn't capture the "+OK" the second attempt did.

Thanks for the info and responding. It's very much appreciated.
It's more than this solution.Get answers and train to solve all your tech problems - anytime, anywhere.Try it for free Edge Out The Competitionfor your dream job with proven skills and certifications.Get started today Stand Outas the employee with proven skills.Start learning today for free Move Your Career Forwardwith certification training in the latest technologies.Start your trial today

From novice to tech pro — start learning today.