Error 0x800ccc90 (POP3 response error - client response invalid)

This error reads as follows:

There was a problem logging onto your mail server. Your password was rejected. Account: '', Server: '', Protocol: POP3, Server Response: '-ERR invalid user or password', Port: 110, Secure(SSL): No, Server Error: 0x800CCC90, Error Number: 0x800CCC92


The first step is to check your Outlook Express settings, making sure that the POP3 and SMTP servers are correct, and that your full username and password are correct.

Then test your connection by following this procedure:

  • Click the Start button, then click Run, and type in cmd (Windows NT/2000/XP) or Command (Windows 95/98/ME). This will open a new command prompt window, with white text on a black screen.
  • Type in the following exactly as it appears. You will not see what you are entering so take it slowly, and if you make a mistake, start again:
  • telnet 110
  • Click the Enter key on your keyboard. You will then be connected to the email server.
  • Type in USER followed by your email address, e.g. USER, and then click the Enter key. You will then get a message +OK.
  • Type in PASS followed by your password, e.g. PASS joblog0370-1, then click the Enter key. If it is correct, you will get an OK Well Done message.
  • If you can do this, you have connected to the server, meaning the problem is with Outlook Express.

If you cannot connect to the server, your password may have become corrupted. Please change it, then try again.

If this doesn't work, it may be that TCP/IP has become corrupted within Windows. Try reinstalling TCP/IP using the following instructions:

  • Click Start
  • Go into Settings
  • Then Control Panel
  • Then Network Connections
  • Right-click your connection, and click Properties
  • Click Internet Protocol (TCP/IP), then click Uninstall

Close down your PC and start it up again

  • Follow the same steps as above, but instead of clicking Uninstall click Install
  • On the screen which appears, click Protocol and then Add
  • Click Internet Protocol (TCP/IP) and then OK (you may be asked for your Windows installation disk at this point)
If you run Windows XP, the process is slightly different:
  • Click Start
  • Go to Run
  • Type in Command
  • In the screen which appears, type in netsh int ip reset c:\resetlog.txt

If you still encounter problems, Outlook Express itself may be corrupt. Please follow Microsoft's instructions on how to delete it and reinstall it, along with making a backup of your address book(s).


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