▷ How to fix Outlook error 0x8004210B in Windows?

Multiple Windows users have contacted us with questions after failing to send emails. After several retries, the operation is interrupted and the following error appears: »(0x8004210B) Operation timed out waiting for a response from the sending server (SMTP / POP3)». When investigating the problem, Affected users report email remains locked in Outbox. Some users report that if they click Submit one more time, the email is sent without problems. The problem is not unique to a certain version of Windows, as it has been confirmed to occur in Windows 7, Windows 8.1 and Windows 10.

(0x8004210B) Operation timed out waiting for a response from the sending server (SMTP)

What is causing the Outlook error code (0x8004210B)?

We investigated this particular error code by searching various user reports and testing different repair strategies recommended by affected users.. It turns out that there are several different scenarios that could trigger this error message. Here is a list of possible culprits:

• Corrupted Outlook Profile: You may see this error message due to a corrupted Outlook email account. If your Outlook profile files get corrupted, Outlook will not be able to communicate with the server. In this case, you should be able to solve the problem by re-adding the email account through the Mail window, which will force the application to create a new profile.

• Email is stuck in send mode: Another scenario where this error code will occur is when the operation expires due to a large or corrupt attachment that cannot be processed correctly. If this scenario is applicable, the only viable solution is to put the application in offline working mode and delete the email that is stuck in the Outbox.

• Reading receipt stuck: in older versions of Outlook, this behavior may also have caused a stuck read receipt. How receipts are invisible in Outlook, there is no way to remove them in a conventional way. In this case, you can fix the problem by using a low-level development tool like MFCMAPI to access your Outlook data store and manually remove the stuck read receipt.

• Third-party AV interference: It turns out that this issue can also be caused by an overprotective AV suite preventing Outlook from communicating with the email server due to alleged security reasons. To prevent this from happening, you should completely uninstall the 3rd party suite and opt for a less intrusive AV suite.

If you are currently having trouble resolving this Outlook error code (0x8004210B), This article will provide you with several different troubleshooting strategies that should solve the problem in most cases. Next, you will find a collection of methods that other affected users have used successfully to resolve the error along with the error message “The operation timed out waiting for a response from the sending server (SMTP / POP3)”.

If you want to remain efficient and minimize intrusions, We recommend that you follow the methods below in the same order that we have arranged them. Since they are ordered by efficiency and gravity, eventually you should find a solution that solves the problem regardless of the culprit that is causing it.

Let us begin!

Method 1: resume your email account

It turns out that one of the most common scenarios that will trigger the (0x8004210B) is a corrupt Outlook email account. Some files belonging to the email account may get corrupted, so Outlook will no longer be able to use them correctly.

If this scenario is applicable, you should be able to solve the problem by recreating the email account one more time from the Mail option in the control panel. Several users who also encountered this issue reported that the issue was fully resolved after following the instructions to re-create the email account.

This is what you have to do:

1. Press the Windows key + R to open a Run dialog. Later, scribe “control” and hit Enter to open the classic Control Panel interface.

2. Once you are inside the classic Control Panel interface, use the search function in the upper right corner of the screen to search “mail”.

3. After doing it, click Mail (Microsoft Outlook) to see the list of results.

4. In the Account Settings window, select the Email tab and click New …

5. Inside the Add account window, enter name, email address and password, then click Next to add the account.

6. Wait until the operation is completed. Depending on your email client, you may be asked to set up the account manually.

7. Once the new email account has been set up, go back to Account Settings> Email and delete the old account (the one that is damaged) selecting it and clicking Delete.

8. Next, select the newly created email and then click Set as default.

Resuming the email account

If the same error code (0x8004210B) keeps popping up even after setting up the new email account, proceed to the next method below.

Method 2: clear the stuck email

In newer versions of Outlook, the most common cause of the error »(0x8004210B) Scheduled operation waiting for a response from the sending server (SMTP / POP3)»Is a situation where the email contains an attachment that contains unsupported or simply too large files.

If this scenario is applicable, you should be able to solve the problem by changing your Outlook mode to “Work offline” and deleting email that is stuck in send mode. After doing it and dealing with the attachment I was having trouble sending, affected users reported that the issue was fully resolved.

Here is a quick guide on how to clear email stuck in Outlook:

1. Open your version of Outlook and select the Send tab / Receive on the ribbon bar at the top of the screen.

2. Next, navigate to the suboptions and click Work Offline once to disconnect your Outlook application from the internet.

3. Once the Internet has been disconnected from Outlook, navigate to the message that previously triggered the error message, right-click on it and choose Delete from the context menu to remove it from your email client.

4. Take care of the accessory, then restart the app and disable work mode.

5. Try sending the email again and see if the issue is resolved.

Clear the stuck email

If you still encounter the error »The operation timed out waiting for a response from the sending server (SMTP / POP3), go to next method.

Method 3: clear the stuck read receipt

Another scenario that will cause the error »(0x8004210B) Timed operation waiting for a response from the sending server (SMTP / POP3)»Is a stuck reading receipt. But the thing about receipts in Outlook is that they are completely invisible in the Outbox, so it is difficult to remove them.

Several Windows users who also encountered this problem have reported that they managed to clear the jammed receipt using a Microsoft support tool called MFCMAPI. Although this is a tool that was originally intended to provide support for “low level” for developers to access Outlook data stores, it is also a useful tool for regular users looking to troubleshoot in an advanced way.

Here is a quick guide on using MFCMAPI to clear the stuck read receipt that is causing the error message:

1. Visit this GritHub link (here) and download the latest version of the MFCMAPI executable. Get the first version if you have 32 bits or get the second if you are using a Windows version of 64 bits. Downloading the MFCMAPI utility

2. Once the download is complete, use an extraction utility like WinZip or WinRar to extract the executable to be run. Remove utility

3. Double click on the executable you just extracted.

4. Once you are inside the MFCMAPI application, go to Session> Login from the ribbon bar at the top. Access the MFCMAPI utility login menu

5. On the next screen, select the Outlook profile you want to edit and click OK. Select the Outlook profile you want to edit

6. Double click on the database that has the Default Store set to True. Access the correct database

7. Once inside the root mailbox, right-click on the top-level folder and choose Open Table of Contents from the context menu that just appeared. Open the table of contents

8. Inside the Reading instance, you should see an item with a subject prefixed »Read:«. Select the read instance, then click on the Actions tab in the ribbon bar at the top and select Submit> Cancel shipping. Cancel the submission procedure

   Note: If you don't see this, means the problem is not due to a stuck read receipt. In this case, go directly to next method below.

9. After doing this, make sure the same entry is selected then go to Actions> Delete message. Next, select the option that says Permanent Delete passing DELETE_HARD_DELETE and choose OK to save the changes. Delete permanently stuck receipt

10. Close all previously browsed windows related to MFCMAPI, then restart your computer and open Outlook to see if the problem is resolved on next system startup.

Once this procedure is done, repeat the behavior that previously triggered the error »Operation timed out waiting for a response from the sending server (SMTP / POP3) and see if the problem has been resolved.

If you still have the same problem, continue with next method.

Method 4: uninstall third party interference (if appropriate)

According to various user reports, this issue can also occur due to an overprotection of the third party AV suite which is blocking Outlook communication with the email server. It turns out that there are several third-party suites that are known to cause this problem in Windows. 10 (including McAfee and Kaspersky).

If this scenario is applicable, you should be able to resolve the error »Operation timed out waiting for a response from the sending server (SMTP / POP3) uninstalling third-party security and making sure all remaining files are removed.

Here's a quick guide on how to uninstall the security pack without leaving any leftover files that can keep causing this error:

1. Open a Run dialog box by pressing the Windows key + R. Once you are inside the Run dialog, scribe “appwiz.cpl” and press Enter to open the Programs and Features menu. Type appwiz.cpl and press Enter to open the list of installed programs

2. Inside the Programs and Features screen, scroll down the list of apps and find the 3rd party AV suite you want to uninstall. Once I can locate it, right click on it and choose Uninstall from the context menu that just appeared. Uninstall third-party antivirus

3. Once the uninstall is complete, follow this article (here) to make sure you don't leave any leftover files that could trigger the same error in the future.