How to fix ‘Fatal Error: 0x80040900’ in MS Outlook?

Aparna Pandey
Aparna Pandey

Updated On - May 7, 2024

Summary: The fatal error 0x80040900 can arise due to different reasons, such as a bad network connection, server timeout, etc. This blog will discuss to fix fatal error 0x80040900 using manual methods and if the methods do not work, then you can go ahead with automated solution, Recoveryfix for Outlook PST Repair. It will surely fix the PST file.

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Users face this fatal error primarily due to server issues, which create problematic situations. Generally, it comes while transferring the mail, and the user cannot send and receive it. It is not just the PST file corruption; improper settings and network problems can even lead to issues in Outlook. For example, many Outlook users suddenly see an error message on the screen.

You would be confused and wonder what the error indicates. What caused it? Before we start discussing that, let’s discuss the possible causes behind the error.

What causes Fatal Error: 0x80040900?

As you are aware, Outlook is configurable with different email services, and you can sync web email accounts like Gmail, Yahoo, AOL, iCloud, etc. You can set up your email account in Outlook either with IMAP or POP configuration, for which you only need details regarding the email server. Well, the email server settings would differ as per the email provider. So, ensuring the email server is configured with the proper settings is crucial. Otherwise, you may encounter a Fatal Error: 0x80040900 message out of nowhere.

Fatal Error: 0x80040900 message out of nowhere

So, you should confirm of the following details are configured correctly:

  • Incoming Mail Server Type – IMAP or POP3
  • Incoming Mail Server Name/Address
  • Outgoing Mail Server Name/Address
  • Incoming and Outgoing Mail Server Port Number
  • Whether Mail Server uses Encryption or not – SSL/TLS

And the above email Server configuration would be different for different servers like, Gmail, AOL, etc.

How to fix the Fatal Error: 80040900?

After understand the various causes. Here, we are going to discuss the various manual methods to fix the Fatal Error: 80040900

Method 1. Review Firewall and Antivirus Settings

Antivirus program gives an option to enable or disable email scanning. If the issue you’re facing is not because of it, you can disable the option and check if the issue persists.

In Firewall Settings, check if either Outlook or the Ports it uses are blocked or not, as per the settings.

  1. Press button to launch Start.
  2. Type Control Panel and press Enter.
  3. Click on System and Security and select Windows Firewall.
  4. Click on Advanced settings.
  5. Here, check for Blocked/Unblocked Ports in both Inbound & Outbound Rules.
Method 2. Check Router

The lousy network connection creates an issue for users accessing their Outlook data files.

  1. An unstable Internet or a faulty Internet router may also cause the same error to happen, and for correcting it, restarting the router would help.
    Check Router
  2. You can restart the Wireless Router by removing it out of the wall; wait for about 20 seconds, and then plug it back and check again.


Login as administer to the router and restart. For doing it effortlessly, find your Router’s IP address, for example,, enter credentials, move to the specific section – as the option to Reboot can be found on different pages for different routers— and click Restart.

Method 3. Checkout server timeout

if the user can send the emails in large-size attachments, the emails may get frozen in our box due to insufficient automatic server timeout. For this, the user can increase the Server timeout value.
Follow these steps to increase the Server timeout:

  1. Go to the Outlook application and open it.
  2. Then, go to the next step, go through the File tab, and click Account Settings > Account Settings.
  3. In the Account Settings tab, click on Change.
  4. Change the Account and click on the More Settings option.
  5. Select the Advanced tab from the window and increase the duration of Server timeout.
Method 4. Use SCANPST.EXE

When configured with POP settings, Outlook will store all the mailbox data on your computer either at the default or specified location which includes emails, attachments, reminder, calendar details, etc. With all the positives there are negatives too, associated with Outlook PST data file. The chances of PST data file turning corrupt or getting damaged are quite common, and there are many reasons behind that can lead to such situation, and data inside Outlook PST file comes on the verge of loss.

limitations of SCANPST.EXE

The built-in utility has some limitations as the tool is available to you free of cost. It is important to understand that, creating software products and services is not free time job; it requires both money and time. So whatever is free, the thing won’t be that good or better in comparison with the paid ones.

  • The utility can’t proceed with repairing large size PST files exceeding 2GB.
  • If Virus or Malware infect the PST file, SCANPST cannot fix that issue.
  • If directory structures & headers of Outlook PST file(s) are broken, then the utility can’t fix it.
  • The utility may stop working in situations when process load is excessive.
  • The utility won’t prove to be any help in cases when the PST file is under the influence of high corruption or is damaged badly.

These are some limitations of SCANPST utility, due to which it becomes hard to tackle the errors faster and effortlessly.

Use automated software

Recoveryfix Outlook PST Repair is the best & advanced tool for fixing all the errors or issues, which you may encounter with Outlook PST data file(s). With RecoveryFix for Outlook PST Repair, you can repair the corrupt or damaged PST data file(s), irrespective of the intensity of corruption or how badly the data file(s) is damaged.

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Also, no matter whether the PST file was under the influence of virus or malware, the tool enables you to repair the file unconditionally and further you can recover the mailbox data.

Maintenance of data structure and hierarchy, no restriction on file size, and cross-platform recovery are some of the exclusive features of the Outlook PST Repair.

Maintenance of data structure and hierarchy, no restriction on file size, and cross-platform recovery

Therefore, whether it is Fatal Error: 0x80040900 or other, you can make use of Outlook PST Repair tool and recover mailbox contents flawlessly.

Additionally, no matter which version of Windows operating system you’re on, Outlook PST Repair tool is compatible with all the versions of Windows available out there, name it Windows 10, 8, 8.1, etc.


Microsoft’s built-in utility comes handy in many scenarios, but not always. If an Outlook error is exceeding the limitations of SCANPST utility then, choosing a more proficient way would be the best thing, and in such scene, Recoveryfix for Outlook PST Repair is the best find.

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