Error 421 is a common SMTP (Simple Mail Transfer Protocol) Outlook error message. MS Outlook is one of the best and popular email applications widely used by PC Windows users for sending and receiving emails within and outside workplaces.
It is most commonly used in offices by professionals for faster communication.
This error may occur while sending and receiving emails on the server. The error 421 messages is displayed in either of the following formats:
“An unknown error has occurred: Server error 421”
"Could not send your message. Error 421"
421 4.2.1 : (DYN:T1) http://postmaster.info.aol.com/errors/421dynt1.html
421 4.3.1 Out of disk space for temp file
421 4.3.2 All server ports are busy
421 Downstream server error
421 Fork failed
421 Greylisting enabled, please try later
“An unknown error has occurred. Subject ‘Testing’, Account: ‘pop.charter.net’, Server: ‘mail.charter.net’, Protocol: SMTP, Server Response:
’421 Message rejected’, Port: 25, Secure(SSL): No, Server Error: 421, Error Number: 0x800CCC67”
Error CausesSome common causes for this critical Outlook error are:
This is a critical Outlook error that should be resolved timely. If you delay, it may cause you a great deal of inconvenience.
The error code 421 hampers your ability to access your email account, send and receive emails, add new contacts, view emails, calendar entries, and journals. In other words, it just brings your email activities to a standstill locking you out of the account.
To resolve this error code on your system, you don’t always have to hire a professional or call the network personnel to do the job. It may be a critical error but the good news is that it is quite easy to fix. Even if you don’t have technical expertise, you can still repair it.
Here are some of the best methods to repair this issue on your system:
Try changing your server settings. Here set the inbound connections limit at the maximum limit.
After the process is complete, try accessing your Outlook email account again; if it works, then that’s great the error 421 is resolved. However, if it doesn’t, then the problem could be related to viral infection.
If the cause of the error is PST files corruption, then not only will you be locked out of your email account, you are also at risk of losing all the data stored in your email account.
However, the best way to resolve the error and ensure full data recovery is to download a reliable PST repair tool. By running a PST repair tool on your system, you can resolve the error 421 right away. It recovers your data, repairs corrupt and damaged PST files.
If viral infection and Trojans are causing the error 421 to pop up on your system, then it is recommended to download and scan your PC with Restoro.
This is an advanced, intuitive, and user-friendly PC fixer. It is not just an antivirus but also a system optimizer and a registry cleaner.
Unlike common antivirus software that only removes viruses and simultaneously slows down the system’s speed, Restoro removes all types of malicious software on your PC including malware, spyware, Trojans, and viruses, and also boosts the speed of your PC significantly.
It is safe, easy to operate, and a quick fixer. It is compatible with all Windows versions.
Click here to download Restoro and resolve error 421 today!

del *.*
Some Windows 7 or Windows 8/8.1 users are having a hard time upgrading to Windows 10 as they are being prompted for a product key. By default, the Windows 10 operating system does not require a product key and users should not be prompted for one, given you upgraded your computer from an activated Windows 7 or Windows 8/8.1 license or from the Windows 10 Preview build. However, there are some users encountering this problem and there are several reasons for this.
Error CausesThere are a few reasons why some users are being prompted for a product key when upgrading to Windows 10:
Before you can fix this problem, you need to know why you’re being prompted for a product key. Some things you should know about Windows 10 product key activation are the following:
Now, if ever you’re prompted for a product key when you’re upgrading to Windows 10, you can apply the following methods:
If you’ve been prompted for a product key upon upgrading to Windows 10, you should click on the “Do this later” option. Wait for a few days then Windows 10 will get activated automatically.
One of the reasons Windows users are being prompted for a product key when upgrading to Windows 10 is that they have downloaded a wrong edition of Windows 10 and do not correspond with your current system.
NOTE: Users of Windows 7 Enterprise, Windows 8.0 Enterprise, and Windows 8.1 Enterprise are not eligible for the free upgrade offer.
If your Windows 7 or Windows 8/8.1 is not genuine or activated, you will get prompted for a product key. You need to make sure first your current system is activated.
Another thing you can try doing is to run the system file checker utility to scan if there are any broken operating system files. In doing so, you’ll be able to detect problems that might be preventing the product activation of your Windows 10 upgrade.
If in case you’ve exhausted all your resources and you are still being prompted for a product key when upgrading to Windows 10, you can try contacting the Microsoft Activation Center for further details. Check here for the appropriate telephone numbers to contact.
If you still experience the error after doing the methods above, you might want to try a powerful and trusted automated tool to fix the job.
“Something went wrong You can contact Microsoft support for help with this error. Here is the error code 0xa0000400.”As you know, keeping your computer up to date with all the Windows Updates is important and is imperative especially if you are experiencing a couple of issues like the Windows Upgrade error 0xa0000400. At the time of writing, there is no specific cause that has been found for this error. However, there are some potential fixes that might help you. You can try to recreate the Windows 10 installation USB and get the ISO files or you could also get a newer version of the Windows Media Creation Tool, or turn off your internet connection at a specific time or run the Windows Update troubleshooter. For more details, refer to the options given below.
In this guide, we will show you common ways in fixing Extended Attributes are inconsistent errors inside your Windows that are easy to do and less time-consuming than complete reinstallation of the system.
Error code 0x000000D1 is a serious error that is displayed when Windows automatically shuts down to protect the system against further damage.
Usually, when this error occurs, the message displayed to the users states something like STOP 0x000000D1 DRIVER_IRQL_NOT_LESS_OR_EQUAL.
What Causes 0x000000D1 Error?Usually, the STOP 0x000000D1 error code is caused by issues like incompatibilities, third-party drivers, driver conflicts, outdated drivers, malicious drivers, and other related problems.
Speaking technically, the message displayed to the user actually means that the kernel-mode driver has tried to gain access to memory at an unreasonably high process IRQL.
If left unfixed, STOP 0x000000D1 error can become quite serious. Increased frequency of occurrence may not only lead to data loss but can cause system corruption as well. That’s why it is crucial to fix it and to resolve the underlying issues causing it as soon as possible.
chkdsk /f /r