How To Repair Outlook Error Code 0x80040900?


To send and receive emails in Outlook, it is imperative to configure MS Outlook account with the name of the server and the appropriate ports. Your Internet service provider provides the server name or IP address ports.

Any flaw or modification in one of the following parameters will completely stop the sending and receiving operations in Outlook. What this means is that you can’t communicate or share information in MS Outlook.

This will result in Outlook Error 0x80040900. If you want to know the reasons behind the occurrence of this error, then here is the list:

Causes of Outlook error 0x80040900:

  1. Limited or no Internet connectivity
  2. Outlook sending and receiving blocked due to a firewall
  3. Incorrect configuration of Outlook account
  4. Worrisome emails preventing you from receiving emails
  5. An antivirus caused issues in the Outlook
  6. Corrupt or damaged office
  7. Reduced server timeout
  8. Third-party plug-ins interfering with the operation of Outlook

The list of causes for the 0x80040900 error could be longer and require a lot of effort and evaluation. However, by scrupulously following the below-mentioned instructions, you can eliminate most of the issues that cause sending and receiving an error in Outlook.

Note: In the Outlook error 0x80040900 repair process, one or more of the proposed resolutions can make your system vulnerable to malfunctions. It is therefore recommended that the user assess the risk and remain cautious before making the suggested modifications.

Step by step guide to fix Outlook error 0x80040900:

Check Internet Connectivity: Before starting with advanced troubleshooting methods, you must check the internet connection. For that, you can open your web browser and check if any website opens or not. If the internet isn’t working, restart the router followed by checking if the status lights are blinking. If not, then contact your ISP

Check email account settings:  If you used automatic account configuration to add your email account, then you can go to the ‘Accounts’ tab under the ‘Tools’ menu to check those. In case, you have manually added your account, then you will have to double-click the email address to check server info, such as incoming and outgoing email server account. If the parameters do not correspond to the predefined values, you will have to re-add the email account by creating a new data file.

Delete all worried or suspicious emails from the inbox: Some of the spam messages target Outlook code macros and therefore interrupt the sending and receiving processes. The next action to take would be to delete any spam you received from prank senders. After cleaning the inbox, you can repair .ost outlook file when using the IMAP account or .pst file when using the POP3 account.

Configure your antivirus to work perfectly with Outlook:Certain antivirus programs are quite extensive and have the ability to end any process that could jeopardize the security of the computer. This could be the reason as to why Outlook OST file can’t open, especially when connecting to the insecure servers. If an antivirus-related plug-in is not listed in the add-ins, check with the antivirus manufacturer’s website to see if a plug-in is required to make Outlook work seamlessly.

Activate all tasks blocked by the firewall: As we all know that a firewall is an anti-malware software integrated into the OS. With any action taken by the executable program (with .exe extension), which the firewall also detects will be blocked temporarily. Run a full virus scan on the Outlook data file before activating Outlook on the Windows Defender firewall.

Go to Control Panel, then System and Security followed by Windows Defender Firewall to get to the screen where you will be able to change firewall settings:

Click on allow an app or feature through Windows Defender Firewallon the left side of the screen.

Note: Please note that any changes to Windows Defender settings may compromise the security of your computer. Therefore, be cautious while making such changes, and it is better to use the solution as the last resort.

Corrupt or damaged desktop: The Office suite of applications has also defined executable program files, which begin or monitor licenses for Office applications such as Outlook, PowerPoint and Word. If the macro file or program files become corrupt or damaged, then it affects the ability of Outlook, which in turn halts the send and receive functionality. Use the following steps to repair your Office application:

Windows 10:

  • On the taskbar, right-click on ‘Start’followed by selecting apps and features. Select the product that you would like to repair in the Office and select ‘Modify’.
  • In case, your Office version displays a message ‘How you want to repair your Office Programs’, then you will have to select ‘Online Repair’. In case, you come across ‘MSI’ based installation menu, then select ‘Change your installation’ followed by ‘Repair’ and then, ‘Continue to repair’.

Windows 8/8.1/7:

  • Go to control panel followed by selecting ‘Uninstall a program’, an option that you can find under ‘Programs’ menu,
  • Locate the ‘Outlook app’ there and once found, right-click on it to find ‘Change’.
  • Now, you need to perform step 2 given in the ‘Windows 10’ section.

Increase server timeout: The server timeout value defines the time the server is going to take until it meets the server request. Lower server timeout values ​​could interrupt the progress while sending and receiving.

For changing the server timeout settings, open Outlook and then, go to ‘File’, then ‘Info’ and followed by‘Account settings’where you can select the email account facing 0x80040900

On the screen, you need to locate the ‘Change’ option. Once found, select the ‘Advanced’ tab to find the server time out setting.

Now, you can change the value, but make sure that the high server timeouts can also sometimes result in issues, so adjust an optimum timeout.

Get rid of any third-party plug-ins added to Outlook:  Before removing the added plug-ins, try to access Outlook in Safe mode followed by checking if its functionality is not affected. Unassigned functionality would mean that third-party apps/plugins are affecting Outlook; you can now remove plugins one by one to identify the reasons behind the problem.


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