Unknown Outlook Error 0X80040201

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Microsoft Outlook used an Outlook PST file to store data like emails, calendars, journals, to do list, contacts and other components while running itself. The transformation of the emails within Outlook processed via protocols, Outlook profile and internet connection. Indeed, any single missing attribute (or improper function of any attributes) of these can raise up the errors in Microsoft Outlook.

In this blog post, we are going to discuss about the Outlook Error 0x80040201 which usually occurs due to the corrupt Outlook profile.

"Sending reported error (0x80040201): 'Unknown Error 0x80040201."

Cause of Error: There is no specific reason for the error code 0x80040201 in Outlook. It can be occurred due to third party plug-ins, enabled scanning softwares, corruption with NK2 file, incorrect SMTP settings, oversized PST file, etc. But, it has found that primarily this error raises up either due to the corrupt Outlook profile or corrupt NK2 file.

Being an Outlook user, if you are getting an Outlook error 0x80040201 on the screen while sending emails through MS Outlook, then I would like to suggest you follow these methods to get rid of from the error code 0x80040201 on screen:

Open Outlook in Safe Mode

Open Run command dialog box by pressing "Windows" button + "R" combine and type the following command "outlook.exe /safe" in it to run MS Outlook in safe mode. By approaching this run command, a user can open Outlook in safe mode without getting any restriction or error message on the screen. Actually, "Outlook.exe /safe" command directly removes the customization from Microsoft Outlook especially customization of third party plug-ins.

Once you will open Outlook safe mode, then immediately disable these third party plug-ins which are interrupting the execution of office (Outlook) program.

If Microsoft Outlook works in safe mode, then disable add-ins by following steps mentioned below and examine the problem causing add-in:

Create a New Outoook Profile

Delete the Cached Outlook Contacts or Delete NK2 File

NK2 file is a kind of dictionary which makes the task of calling an email address more easier by endowing the email address by itself to Outlook users. Means, you don't need to type the entire email address while sending messages as Outlook creates an NK2 file to save all the contacts which have used earlier by a program. Here, I am talking about the contacts which are not saved as Outlook contacts. This file only stores cached contacts of Outlook which would have been used by Outlook users or Outlook admin to send or receive emails in the past.

Corruption in NK2 file is as also one of the prime cause behind the Outlook error 0x80040201. So as a resolution either we have to remove each of the cached contacts manually from the Outlook or we can solve this bug directly by deleting the NK2 file after reaching out it from its default location.

Location of NK2 file in Outlook: %APPDATA%\Microsoft\Outlooks

Copy and paste the above given location in the Window's address bar and it will directly move you at the default location of NK2 file.


If you are looking for a permanent solution to troubleshoot Outlook Error 0x80040201, then you can apply these methods one by one to get the solution. Explicitly, it is not compulsory that these methods will surely fix the error and re-starts the proper functioning of send/receive. If the corruption level is high and it have been impacted the Outlook Data File, then there is a need to think about the repairing of it or go for any advanced trustworthy tool like Outlook File Recovery.