Resolved: Sending Error 0x80040201 in Microsoft Outlook

Outlook error 0x80040201 is a quite common sending failure error that appears when Outlook is unable to deliver an outgoing email message. It could be due to corrupt auto-complete entry, antivirus conflicts, damaged PST file, or other issues. The error message appears as Sending' reported error (0x80040201) : 'Unknown Error 0x80040201'.

It means Outlook has failed to process the send request at the MAPI level. Unlike typical SMTP errors, this error is not related to your mail server settings. But this error usually pops up without giving any specific reason, which makes it difficult for the users to identify the actual cause of the problem.

What Causes Outlook Error 0x80040201?

The Outlook error 0x80040201 may occur for multiple reasons. Knowing the exact cause can help in easily resolving the issue. We have mentioned some possible reasons along with their solutions:

1. Faulty Third-Party Add-ins

Outlook users install and add third-party add-ins to the Outlook application for convenience, but sometimes these add-ins interfere or affect the normal functioning of the Microsoft Outlook application. In that case, the removal of the add-in from the application is essential to fix the issue.

To disable faulty add-ins from the Outlook application, first, Outlook needs to be run in the Safe mode. For this, press the Windows key and R alphabet together to open the Windows Run box. Then type outlook.exe/safe and click on OK.

Now, the Outlook application gets opened in the safe mode. After this, follow the given instructions.

1. In Outlook, click File > Options.
2. Click Add-ins, then go to the Manage drop-down list and select COM Add-ins. After selecting, tap Go.
3. Uncheck all Add-ins, then click OK.
4. Restart the Microsoft Outlook application and enable add-ins one by one to identify the faulty add-ins.

Note: Repeat the process until you find the faulty add-in and remove it.

2. Interference of Third-Party Antivirus/Firewall

Third-party antivirus or the system Firewall may block requests sent by the system to other applications like Outlook and block many functions or services, leading to different types of errors.

To handle interference from antivirus, Anti-malware, or Firewall, temporarily disable all these services and then restart the Outlook application once to check if it was the cause behind the error.

3. Auto-Complete List Cache File

Whenever you type an email address, Outlook shows suggestions from your previously used email addresses. This list is stored in a hidden cache file in your Outlook profile. Sometimes, it may contain corrupted, old, or incorrectly encoded data. These issues with the cache file may cause the Outlook error 0x80040201. Emptying the Auto-Complete List cache file may help you resolve this error:

1. Launch the Microsoft Outlook application.
2. In Outlook, go to File > Options.
3. In the left panel, choose Mail, then in the right panel, go to the Send messages section and click the Empty Auto-Complete List.
4. Click Yes on the confirmation message.
5. Finally, restart the Microsoft Outlook application.

Note: All modern desktop and web-based Outlook versions include the AutoComplete list feature, including Microsoft 365, Outlook 2021, 2019, 2016, 2013, 2010, Outlook on the Web, and New Outlook.

4. Corrupt Cached Outlook Contacts File

When the Outlook users disconnect the Exchange Server and start using a local PST file, the contacts in Global Address Lists may still be there in the corrupted form. It can result in the Outlook sending error. The exact reason for the error is a corrupted cached contacts file, also known as the NK2 contacts file.

As the cause is a corrupted cached contacts file, also known as the NK2 contacts file, it is necessary to delete these files first.

Note: Microsoft Outlook 2007, 2003, 2002 (XP), and 2000 use the NK2 contact list.

Navigate to the location - C:\Users\Username\APPDATA\Roaming\Microsoft\Outlook

Look out for the Outlook.NK2 file and delete it from there. Close the window and restart the Microsoft Outlook application.

5. Corrupted Outlook Data File

It is good for users if they can get rid of the Outlook errors by using the above-mentioned solutions. But if no success has been attained yet, then the problem must lie in the Outlook profile or the Outlook PST file, i.e., corruption.

The Outlook profile can be easily created again from the Control Panel and can be set as the default one. Here are the steps to do it:

1. Open Outlook, then click on File > Account Settings > Manage Profiles.
2. Click on the Show Profiles button.
3. Moving ahead, click on the Add button.
4. Provide a Profile Name and click OK.
5. Enter Name, Email Address, and Password, then click on the Next button.
6. Finish setting up the new profile, select Always use this profile (make sure to select the new profile from the drop-down menu), and click OK.

What to Do If Outlook Error 0x80040201 Keeps Coming Back?

Even after trying all the manual methods, the issue persists; it might be due to a heavily corrupted PST file. If you have a large PST file, then the inbuilt repair solution scanPST.exe may not be able to resolve PST corruptions of high level as it can only fix minor PST corruption issues.

In such a scenario, we suggest using Kernel for Outlook PST Repair to fix all types of corruption issues in the PST files. The software deeply scans the corruption and retrieves all recoverable data items from the PST file. It offers a detailed preview of the source file before saving to make sure all the data is present in the file. Moreover, it is an offline and read-only tool, keeping all your data intact.

Ending Lines

Outlook error 0x80040201 may seem like a complex problem, but it can be fixed by resolving a few simple issues, such as deleting a corrupt auto-complete list, removing faulty add-ins, or recreating or repairing PST files. And if the PST file is severely corrupted, using an advanced tool will be the best solution.

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