What is the error code 0x800ccc90?
The 0x800ccc90 is a common Outlook Express error. This error occurs when Outlook Express fails to connect to the mail server that handles incoming and outgoing emails.
The error is usually displayed as:
“There was a problem logging onto your mail server. Your User Name was rejected.”
Though this error does not pose any security threats to your PC if it is not fixed immediately, it may limit your ability to send and receive emails on your Outlook email address.
Error Causes
The error 0x800ccc90 is usually triggered by the following causes:
- Authentication problem- This happens when your account details are not authenticated by the server. In this case, you will see a pop up message displaying ‘Server:’pop3.example.com’, or ‘Secure (SSL): No, Server Error: 0x800ccc90’.
- Failure of POP3 server
Further Information and Manual Repair
If you come across the error 0x800ccc90, then don’t you worry! You don’t have to hire a professional to resolve this issue. In fact, you can fix it all by yourself. Here are some DIY solutions to repair this problem.
Solution 1:
- Go to the ‘Tools’ tab and select ‘Accounts’
- As you click on the accounts tab, an internet accounts box will appear on the screen
- Now double click on the account property box.
- After that go to the server tab and click it.
- Now check on the box that says ‘My Server Requires Authentication.’
- Once you check on this option now click on apply to accept changes and then close the window.
- To bring the changes into effect, restart Outlook and then try to send emails again. Hopefully, this will work.
Solution 2:
However, if you are still unable to resolve the problem, then this means the PST files are corrupt and damaged and there is no problem from the server's end. When this happens, then the best way to resolve this problem is to download a PST repair tool.
We suggest downloading the PST repair tool from a trusted website.
After downloading it, run and scan it on your PC to detect errors. You will have to be patient because scanning may take a couple of minutes. Once the scanning is complete, click on repair to resolve the problem.
So, next time when you are unable to send or receive emails on your Outlook Express and you see the 0x800ccc90 error message, then try using the solutions given above to resolve the error right away.


Tracked as CVE-2021-34484, the “zero-day” flaw enables hackers to breach all versions of Windows (including Windows 10, Windows 11, and Windows Server 2022) and take control of your computer.
Microsoft mistakenly thought it had patched the vulnerability (which was first found in August) when it was publicly disclosed in October. But the fix itself was found to be flawed, something the company admitted, and this drew even more attention to the vulnerability. Microsoft subsequently promised to “take appropriate action to keep customers protected” but two weeks later, a new fix has still not arrived.
Luckily the third-party security specialist 0patch has beaten Microsoft to the punch with a ‘micropatch that it has now made available for all Windows users “Micropatches for this vulnerability will be free until Microsoft has issued an official fix," 0patch confirmed.
You will need to register for a 0patch account and install its download agent before the fix can be applied, but with 0patch fast becoming a go-to destination for hot fixes which beat software companies to the punch this is a no brainer. Hopes will be high that Microsoft can release an effective patch sooner rather than later but, until then, all Windows users must act now if they want to be safe.
Download 0patch here:
For many people that are playing online games, this is not such a big deal since they always must have the latest version in order to play their games but for other ones, this has arrived as a bit of a problem. Many people preferred older game versions since often updates can change certain mechanics inside the game making it different as an experience or introduce some elements that not everyone likes.
So far, people could use the steamDB site to find depo of the game versions you would like to play and download it but if this beta code goes live that will not be an option anymore. Now, playing old games without updates could also be used for nostalgic reasons and these people have also been cut off with this update.
It is important to point that update is still in beta client only but users have already started to voice their opinions asking Valve not to place it live. In the end, it will all depend on Valve’s decision will they listen to their customers or decide to push updates on live service. 