5 Solutions to Fix Outlook Error 0x8004210b

Amy Dennis

Apr 07,2020 • Filed to: Recover & Repair Emails • Proven solutions

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Users have been complaining of inability to send emails on Outlook. The Outlook error message that pops up after trying several times is shown in the image below:

As it turns out, you may be a user with this challenge looking for answers. Well, you have come to the right place for answers. In this article, you will learn all about the error message 0x8004210b, the causes of the error message, and the top five solutions to fix the error. The most important solution is saved for last so carefully go through the solutions to find what you need.

What is this Error Message?

As stated in the description above, Outlook error 0x8004210b is quite common among users of Outlook. However, what exactly does it mean when a user sees this error message? As a user, if you see this error message, it means that the remote server which stores your emails in Outlook is taking too long a time to retrieve or get your emails to be sent. Other symptoms associated with this error are periodic system freeze, system crash or crash of active program window.

Finding the Causes of Microsoft Error Message 0x8004210b

The following are some of the causes of the error message 0x8004210b:

• Corrupt Windows Registry: If you recently made changes in your software and you begin to experience this error, it could be that your recent changes have caused Windows Registry to get corrupt, thereby leading to the error 0x8004210b
• Corrupt Outlook Profile: A corrupt Outlook profile can be a major cause of this error. It is only logical that if an email account is corrupt, every other operation associated with such an account gets affected.
• Interference from Third-Party Antivirus: If the antivirus program you have installed is suspecting some security issues, it can become overprotective and stop your Outlook from communicating with the email server.
• Incomplete Outlook App Installation: This error can occur if you did not install the Outlook app completely or properly. It can also come from a corrupt installation of Outlook

How to Fix the Reported Error 0x8004210b in Microsoft Outlook

1. Make sure that you are connected to the internet and able to telnet SMTP port number

Your SMTP port 587 or 25 may be blocked by a firewall or your Internet Service Provider (ISP). So, check that you still have an internet connection and telnet on port 25. The steps below will guide you in doing this:

• Open a browser or ping www.google.com. A reply like below should come up



• In the address bar, input either of these addresses:
  http://www.msn.com
  http://www.microsoft.com
• Now, press “Enter” on your keyboard and check for any proxy settings

To telnet the SMTP port number, do the following:

• Open the “Run” dialog window by pressing down the “Windows” and “R” keys at the same time. Type the command “CMD” in the box and click “OK”



• Let the command you type be telnet smtp.servername.com 25
• The reply in the image below will pop up. If this does not happen, then you should contact your ISP

2. Check the Outlook email account settings

Check to ensure that your email account settings are correct by following the steps below:

• Under “Tools”, select the option “Account Settings”



• Double click on the email address in question after selecting “Email”



• Now select “More settings”



• Under the tab “Outgoing Server”, click the checkbox beside the option “My outgoing server (SMTP) requires authentication”



• Change the port number in the box next to “Outgoing Server (SMTP)” from 25 to 587

3. Disable or uninstall anti-virus

Third-party anti-virus programs can cause this error through their interference of your attempts to send emails. You can resolve this issue by uninstalling or disabling the programs through the following:

• Open the window “Run”. To do this, use the shortcut “Windows” key plus “R” key. In the dialog box, input the instruction: appwiz.cpl.



• This will lead you to “Programs and Features” once you press “Enter” on your keyboard



• Search through the applications list to locate the third-party antivirus program you wish to uninstall. Right-click the program once you find it, and tap on “Uninstall” from the menu that pops up.

4. Install available Windows update

Your Windows may be outdated, thereby causing this error message. With the steps below, you can set your system in such a way that whenever a Windows update is required, it will automatically go through:

• Using Windows 10 as an example, choose “Start” menu
• Click on “Update & Security”



• Select “Windows Update”
• Once you check for updates, it will automatically update if there are any available ones.

5. Try Outlook repair tool

Some errors run deep and cause more damage than normal troubleshooting can handle. It might seem like all hope is lost after you have tried the above solutions to no avail. You can always try an Outlook repair tool to resolve this issue. Stellar Outlook Repair is the professional tool that is capable of handling all your Outlook repair needs. With this tool, you can fix any error in your PST file on any Windows version you are using. It supports files repairs in different types of folders such as attachments, journals, calendars, schedules, etc.

To use Stellar Outlook Repair tool after downloading, do the following:

Step 1. Add Corrupt File

Open the home interface of Outlook and add the corrupt PST file using the buttons “Find” or “Browse”

Step 2. Repair Corrupt File

Start the scanning process by choosing “Repair”. Watch for the progress window

Step 3. Preview and Save File

Preview the files that have been repaired above once complete

Now go to the “Home” menu on the display bar and click “Save Repaired File” from the drop-down list

The Bottom Line

This error 0x8004210b occurs in different versions of Windows like 8.1, 7, 10, hence it affects a wide range of users. However, with the key solutions in this article, you can fix the error and go-ahead to send that all-important email without any delays. Most importantly, you can trust Stellar Outlook Repair to fix all issues related to your Outlook PST files.