Top 5 Tips to Fix Error 0x8004210b in Outlook – Updated

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Summary: Are you struggling with the Outlook error 0x8004210b? If yes, you need to read this write-up carefully. Here, we will explain to you what the error message means, what are the reasons and how to fix the error message?

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What ‘Sending Reported Error (0x8004210b) Outlook Error Indicates?

Sometimes, when you try to send or receive an email through Outlook, you receive the following error message as the remote server is taking time to send new emails.

“Sending’ reported error (0x8004210b): The operation timed out waiting for a response from the sending (SMTP) server.”

As the error states, the Outgoing server (SMTP) takes too long to respond. It means Outlook is unable to establish a secure connection to the server.

Now, there are many reasons for this problem. Let us have a look at some of the most obvious reasons that cause error 0x8004210b Outlook 2016.

Why Does the Microsoft Outlook Error 0x8004210b Message Appear?

Like any other Outlook error message, Outlook sending error 0x8004210b occurs due to various reasons. As this problem arises because the outgoing server is unable to establish a secure connection, anything which is blocking the connection causes the Outlook issue.

Some of the most common reasons are

#1. Damaged Windows Registry

Windows Registry contains the configuration settings of the Windows Operating System. Any modification in these settings may affect the working of various applications. Sending Reported Error (0x8004210b) in Outlook is one of the consequences of changes made in Windows registry keys.

#2. Blocked SMTP Port (25 and 587)

The Outgoing SMTP server ports are 25 and 587. If these ports are blocked by your Internet Service Provider (ISP) or Firewall, you will encounter this error.

#3. Faulty Outlook Profile

Another most obvious reason for 0x8004210b in Windows 10 or other versions is the corrupt Outlook profile. You need to delete the faulty profile and add it again.

#4. Hindrance by Outlook Add-ins

Some Outlook add-ins hinder the proper functioning of Outlook applications. They stop the Outgoing to establish a secure connection.

#5. Corrupt Outlook Data File

When the Outlook data file gets corrupted, it becomes impossible for Outlook to fetch the mailbox data. Also, it is among the reasons for the Outlook error message.

These are some of the most significant reasons for the sending reported error 0x8004210b in Outlook 2019. Now, it is time to explore the solutions to this error message.

Also Read: Top 10 Outlook Errors and How to Fix Them – Useful Insights

How to Fix the Outlook Error 0x8004210b?

Depending upon the origin of the problem, there are numerous ways through which you can fix the error message. However, to perform the techniques you must have a decent knowledge of Outlook and its features.

#1. Complete Scanning of System using Antivirus

The first thing you can do to fix the Outlook error is to run a complete scan. It may be possible that the problem occurs due to some virus attacks. Windows provides you with a built-in antivirus to protect your system. Follow the below steps to run a quick system scan.

  • Click on the Start button and press the Settings icon.
  • Now, choose the Update and Security option.

Update and Security option

  • After that, switch to the Windows Security tab.

Windows Security tab

  • Click on the Virus and Threat protection option.

Virus and Threat protection option

  • Hit the Quick Scan button and wait till the scanning completes.

Quick Scan button

  • After completing the scanning, you need to perform the required options to fix the problems.

The above technique will resolve the issue. However, if the remains, you can adopt the other solutions.

#2. Check and Update Windows Drivers

You might require to update the device driver to resolve the Outlook error 0x8004210b. Below are the steps to update the device driver.

  • Right-click on the This PC option and select the Manage options.
  • Now, in the Computer Management system, click on the Device Manager option.

Device Manager option

  • Expand the desired category to check its options. Right-click on any item.
  • Right-click on any item and choose the Update Driver option.
  • After that, select the desired options and proceed further.

#3. Reconfigure Outgoing Settings

  • Launch MS Outlook in your system and click on the File button.
  • Click on the Account Settings icon.
  • Select the Account Settings option from the list.
  • Now, double-click on the desired email address to modify its settings.
  • In the Email account wizard, click on the More Settings button.
  • Switch to the Outgoing Server, tick the My Outgoing server (SMTP) requires authentication option.
  • Now, in the Advanced tab, fill in the Outgoing Server (SMTP) to 587.

Outgoing Server (SMTP) to 587

  • Press OK to save the changes.

#4. Disable Faulty Add-ins in Outlook

  • Open the Run wizard and type Outlook /safe in the field and press Enter.
  • It will open Outlook in safe mode without additional add-ins.
  • Now, click on the File button and choose the Options tab.
  • In the Outlook Options dialogue box, select the Add-ins tab.

Outlook Options dialogue box, select the Add-ins tab

  • Click on the Go button in front of the Manage option.

Manage option

  • Now, disable all the add-ins and press OK to save changes.

add-ins and press OK to save changes

  • After that, enable each add-in one by one to identify the faulty add-in.

#5. Repair Damaged Outlook Data File

One of the most common reasons for error 0x8004210b messages in corrupted Outlook data files. Outlook provides you with an inbuilt tool, scanpst.exe, using this, you can repair the damaged Outlook file. Let us check how to repair the corrupt Outlook file.

  • Open File Explorer and go to the following location.

C:\Program Files (x86)\Microsoft Office\Office16.

Note: This location is for Outlook 2016 for 64-bit operating systems.

  • Launch the application and click on the Browse button to choose the desired file.
  • After that, press the Start button to start the scan.
  • Now, after completing the scan, click on the Repair
  • It will repair the damaged Outlook data file and hence the Outlook error.

All the above solutions will help you fix the Outlook error 0x8004210b. Every method corresponds to a specific reason for the error message. So, if you are facing the Outlook issue due to the above-mentioned reasons, these techniques will surely help you out.

What if the Problem Persists due to a Damaged Outlook Data File?

Sometimes, the Outlook data files are heavily damaged such that the inbuilt SCANPST.exe becomes unable to repair the file. In such cases, you will require a professional tool that can fix any level of corruption.

DRS PST Recovery Tool is the best solution to repair any level of Outlook data file corruption and hence resolve Outlook errors. This prominent utility has all the advanced features to recover the maximum possible data. Moreover, the application is easy to use such that a novice can use the application efficiently.


There are numerous reasons for Outlook error 0x8004210b and so are the solutions to fix this error message. One of the most common reasons for this Outlook ‘Sending Reported error (0x8004210b)’ is the damaged Outlook data file. The most recommended solution to repair a damaged Outlook data file is the professional Outlook Repair Tool.

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