Outlook Fatal Error – Know How to Resolve It

outlook fatal error

We know that Outlook PST corruption played a substantial part in Outlook workflow, but this is not the only cause of Outlook unresponsiveness. Outlook Network issues can also result in errors like Outlook fatal error or fatal error 0x80040900.

Furthermore, if you are experiencing the same issue in your Outlook software and want to resolve it, we will explore the causes as well as a way to resolve Outlook fatal errors in this article. But, before we get to the solution, let’s first define fatal error 0x80040900 in Outlook.

What is Outlook Fatal Error and Reasons for this Error

As we all know, Outlook allows you to configure many email services, as well as sync web email accounts such as Gmail, Yahoo, AOL, iCloud, and others. In addition, you may configure your email account in Outlook using either IMAP or POP settings, which requires simply the email server’s data.

Now, when we talk about email servers, they are also distinct for different email clients. As a result, it is critical to ensure that the email server is set up correctly. Otherwise, you may receive an unexpected Fatal Error: 0x80040900 message. Furthermore, always double-check that the following details are accurately configured.

  • Incoming Mail Server Type IMAP or POP3
  • Incoming Mail Server Name/Address
  • Outgoing Mail Server Name/Address
  • Incoming and Outgoing Mail Server Port Number

How to Manually Repair Outlook Fatal Error

Here in this section, we are going to elaborate on some tested techniques that will help you fix this same error.

#Method 1: Reset Firewall and Antivirus Configurations

There are several antivirus programs that provide an email scanning capability, which may be the cause of a fatal error in Outlook. So, if your antivirus software has an email scan option, disable it. Whether the problem is not caused by it, you can disable the option and see if the problem remains.

Check the Firewall Settings to see if Outlook or the ports it uses are banned or not.

1. First, press the Start button.

2. Now, type Control Panel and hit the Enter key.

3. After that, pick Windows Firewall from the System and Security menu.

4. Now, select Advanced settings.

5. In this section, look for Blocked/Unblocked Ports in both Inbound and Outbound Rules.

#Method 2: Check for the Internet Connectivity

One of the most prevalent causes of Outlook’s fatal error is this. Because an unreliable Internet connection may also result in the same problem. To resolve this, contact your ISP or restart your router.

#Method 3: Repair Outlook PST File to Resolve Fatal Error 80040900?

We know that if you setup your Outlook account in POP settings, Outlook will save all mailbox data on your computer, whether at the default or selected location, including emails, attachments, reminders, calendar entries, and so on.

With all of the benefits, there are some drawbacks to using the Outlook PST data file. The possibility of a PST data file becoming corrupt or damaged is extremely common, and there are several causes that can lead to such a situation, and data contained within an Outlook PST file is on the edge of being lost.

Well, there are a few options for resolving the problem, including both manual and automatic ways. The first is SCANPST.EXE, a built-in program offered by Microsoft. You can try to repair the PST file problem with the SCANPST software.

Limitation of the Scanpst.exe Tool

Because the tool is free, there are certain limits to the built-in utility. However, we must recognize that time and data are more valuable than money.

  • The software is unable to repair huge PST files larger than 2GB in size.
  • If a virus or Malware attacks the PST file, SCANPST will not be able to repair it.
  • If the directory structures and headers of the Outlook PST file(s) are corrupted, the software will not be able to repair them.
  • When the processing demand is too high, the utility may cease operating.
  • The application will not be of any use if the PST file is heavily corrupted or severely damaged.

These are some of the limitations of the SCANPST application, which make dealing with mistakes difficult.

The Most Effective Way to Repair Outlook PST Corruption

When you get the Fatal Error: 80040900, you should attempt the Scanpst program right away. However, if the PST files are severely corrupted, this procedure will not work.

If the level of corruption is extremely high or the PST file has been corrupted due to the influence of a virus or malware, there is nothing you can do with the SCANPST tool. To remedy this scenario, use the Outlook PST Repair Tool. It is one of the most effective methods for repairing Outlook file corruption. Let’s have a look at some of the tool’s more advanced features.


Well, it is time to wrap up the thing, we have discussed all the possible ways to fix Outlook fatal error. Now, if you are going through this error, then read out the blog and fix the Outlook 80040900 error.

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