0x8004210B Error Solved in Microsoft Outlook 2016, 2010, 2007

Summary: If you are getting an error message that states the issue -Microsoft Outlook Error message 0x8004210b, then no worries just read this article as all queries will be solved. Generally, MS Outlook allows its users to open their previous emails without needing an Internet connection. These messages can be downloaded later. Users can send or receive emails once it is connected to the internet.

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But what if one receives an error message? The main reason behind these error messages is due to the inappropriate email configuration that leads to this error. 

In technical language, this error happens if the user’s ISP or firewall in their PC obstruct SMTP port 25 or 587. Users can inspect this Sending reported error (0x8004210b) by telnet on port 25 on their domain.

This type of error usually occurs during sharing (send or receive) emails. It simply signifies that the server is consuming a lot of time to get or send new emails.

Possible Factors of Microsoft Outlook Error Message 0x8004210B

  • If the Windows Registry is corrupted because of the recent changes in Software.
  • Because of the Malware or Virus attack 
  • Sudden or maliciously deleted Outlook files.
  • Install of Outlook application in an Inappropriate 

DIY Strategies to fix if Sending reported error (0x8004210b):

Suppose user A gets an error message then he should perform these steps that are given below. 

1. Inspect the Internet connectivity:

 If a user receives a Microsoft Outlook Error message 0x8004210b. Then, the first thing to do is to check Internet connectivity. Then, users should seek and open any browsers such as Internet Explorer, Google Chrome, and also browse for multiple websites. This process will ensure the users if the websites are opening. Users can continue with the other steps.

2. Try Telnet SMTP port number:

If one wants to inspect the Simple Mail Transfer Protocol (SMTP) communication between messaging servers then try Telnet. This will help the user to fix the error of sending or receiving messages. By this process, users can send their SMTP commands manually to a messaging server.

Users have to perform these steps that are mentioned below.

  • First, launch Command Prompt by the Admin privileges.
  • Then, enter the telnet command line on the elevated command prompt – telnet smtp.servername.com 25.

For example – if the user uses a Google account then, the telnet command – telnet smtp.gmail.com 25.

  • Then, make a replica of the below command, paste it in Command Prompt, and tap enter.

 Next, the user should view the screen below. If it is not, then try to contact the Internet Service Provider.

Inspect the working of Outlook. If the problem still exists then, continue with the other resolution steps.

3. Inspect the Outlook email account settings:

  • Firstly under the “Tools” menu, tap on the “Account Settings”.
  • Now, tap on the “Email” and press double tap on the email address from which the user is unable to send emails.
  • Once pressed the double-tap, the user can view another pop-up Window. Tick on “More Settings buttons”.
  • Set the option “My outgoing server (SMTP) requires authentication” checkbox from the Outgoing Server tab .
  • Make adjustments in the port number from 25 to 587 on the Outgoing Server (SMTP).

4. Use the Antivirus to scan the System 

These errors generate due to a virus, trojan that infects user’s files. Users should operate a full malware scan of the system through an antivirus program.

5. Repair Outlook

You can try repairing MS Outlook. If you are a technical expert, you can use Microsoft tools first. Otherwise, you can try user-friendly third-party tools such as Outlook PST Repair Tool.

The Indicators that confirm the error:

  • If the active program window crashes
  • If the system crashes along with Error 0x8004210B
  • When the Windows works sluggishly and also responds, the time of the mouse or keyboard becomes slower.
  • If the system often freezes in every short period.

Outlook Error 0x8004010F: Read Here


This blog explained the solutions that one should follow if they receive an error message- Microsoft Outlook Error message 0x8004210b. These messages generally appear while installation of a program, Windows shutdown, or installing Windows operating systems. This is a guide for those who are either beginners or who do not belong to the technical background. Users should perform this process with care so that they can avoid data loss. 

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