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How to Fix the Outlook Error Code 0x800ccc78?

How to Fix the Outlook Error Code 0x800ccc78?

Outlook Error Code 0x800ccc78

If you are facing the Outlook Error Code 0x800ccc78 then you would be glad you came across this blog. Here you will find the all solutions to resolve the error encountered in your Outlook. Nevertheless, before we begin with the process let us first look into what this Outlook error is about and why it occurs.

The Outlook Error Code 0x800ccc78’ is one of the Outlook errors which appear when you try to send or receive new emails and meeting invites. This error also prevents you from making any other changes to Outlook such as moving or deleting messages from the mail folders.

So when you try sending a new email or manually update folders to receive new emails, Microsoft Outlook fails to operate and thus you see the following error message displayed on your screen;

‘Sending’ reported error ‘‘0x800ccc78’; cannot send the message. Verify your email address in the account section. The server responded – 550 access denied ‘Invalid Helo’ name (see RFC2821 4.1. 1.1)’

You will find that the error in Outlook is often accompanied by the following issues:

  • The inability to send or receive new messages or emails
  • Outlook freezing stops responding or crashes frequently
  • Slow performance
  • Outlook takes longer to load or display search results
  • Failure to access the calendar or other Outlook features

Below you will learn all the reasons that can trigger the 0x800ccc78 error in Outlook as well as the topmost solutions that will help to troubleshoot and resolve the issues effectively.

What are the Reasons for Outlook Error Code 0x800ccc78?

Well, there are several reasons that could trigger the error 0x800ccc78; these also include the following:

  • Incorrect or outdated email settings
  • Issues with Authenticity due to network connection or an expired password
  • POP (SMPT) mail server-related errors
  • An outdated Outlook
  • Facing conflict with other programs such as antivirus
  • Damaged or corrupted PST file
  • Large or oversized PST files
  • A corrupted profile
  • Any faulty or incompatible add-ins

Solutions to Troubleshoot and Resolve the Outlook Error Code 0x800ccc78’

As you read along you learn about some of the topmost solutions that you can apply to troubleshoot and resolve the Outlook Error Code 0x800ccc78.

Solution 1: Check the Network Connection

You should remember that an unstable or poor network connection on the client machine or server can prevent Outlook from communicating or even making a stable connection with the mail server. In this condition, it can lead to the error ‘0x800ccc78’. Hence it is very important that you make sure to have a stable network connection.

To check and troubleshoot the network issues you should follow the steps below;

  • You must first try and connect to a different Wi-Fi (wireless) or wired network
  • Check and then also reconnect the Ethernet cable
  • Restart the modem or the router
  • Disable the VPN if available
  • Remember to Change the DNS to and
  • Also, open a web browser window on your system and visit any site to check whether the internet is working properly
  • Try logging in to the webmail version (webmail.yourdomain.com or similar) and make sure that the server is online and available

Solution 2: Double-Check Email Settings

Keep in mind that you must verify your username, password and SMPT server details and also ensure that they are correctly configured. To do so follow the given steps;

  • Firstly, in Outlook 2013 and later, you need to go to ‘File > Info > Account Settings > Account Settings’.
  • In Outlook version 2010 and earlier you will need to go to ‘Tools > Account Settings’.
  • After that, under the ‘Email’ tab, you have to click on your POP email account and then click on the ‘Change’ button. Here you could also double-click to open more settings.
  • Now in the ‘Change email account’ window you need to check and update the details such as login username, and password and then click on ‘More Settings’.
  • Next, right under the ‘Outgoing Server’ tab, you should check the ‘My outgoing server (SMPT) requires authentication’ option.
  • After which you need to select the ‘Use same settings as my incoming mail server’ and then just click on OK.
  • You would now need to restart Outlook for the changes to take effect and then try and send emails.

Solution 3: Verifying the Port Number

You should know that a wrong port number can also lead to a failed connection with the mail server, which can result in the error 0x800ccc78. Follow the mentioned steps to fix the error;

  • You need to start by opening ‘More Settings’ (as mentioned above) and then click on the ‘Advanced’ tab.
  • Next, you would need to check that the ‘SMPT port’ number is correct.
  • Now if you are not sure or you do not know then you could contact your administrator to learn more about the right port number and then just enter it in the given field.
  • After that, you just need to click on the OK button and restart Outlook.

Solution 4: Disable the ‘Secure Password Authentication’

  • Now in Outlook 2010 and earlier versions, you will need to click on ‘Tools > Account Settings’. And in Outlook 2013 and later versions you would need to click on ‘File > Info > Account Settings > Account Settings’.
  • After that, you will need to double-click on your email account and then click on ‘More Settings’.
  • Next, under the ‘Security’ tab you need to remove the tick from the tick box that says ‘Always prompt for logon credentials’. Then in the ‘Servers’ section, you must uncheck the ‘Log on using Secure Password Authentication’ (this varies based on your Outlook version).
  • And now you just need to click on the OK button.

Solution 5: Check and Install the Latest Updates

Here you got to make sure that you’re Outlook and Windows are updated to avoid any incompatibility issues or bugs that may have triggered the error. Follow the steps below to fix it;

  • You need to first open Outlook and then click on ‘File > Office Account’.
  • Next, you should click on the ‘Update Options’.
  • And then from the options, you need to click on the ‘Update Now’ button.
  • Now if new updates are available then you should download and install them immediately.
  • When the updates are installed then you will need to restart Outlook (you could also reboot the system) for the changes to take effect.

Likewise, you can open ‘Settings > Updates and Security’ on your system and then just check and install Windows Updates.

Solution 6: Check Conflicts with Other Programs

Furthermore, Outlook could also conflict with other programs on your system such as the antivirus which leads to the error 0x800ccc78. To fix this you should follow these steps;

  • You will need to disable your antivirus or anti-malware temporarily. After which you should restart Outlook and check if the error continues.
  • Now if the error has been resolved then you need to make sure to add Outlook as well as the PST files as an exception in the antivirus.
  • However, in case this doesn’t work then you can contact the antivirus support for more help or you could install Outlook aware antivirus software.

Solution 7: Disable the Add-ins

Do you know that you can disable the add-ins in Outlook to see if they are the cause of the error? Just follow the steps below;

  • You must first run Outlook in safe mode; to do so you would need to press the ‘Windows + R’ keys, then type outlook.exe/safe and then just press the ‘Enter’ key.
  • After that, you will need to go to the ‘File > Options.’
  • Next, you should click on the ‘Add-ins’ and then click on the ‘Go’ button at the bottom, beside the ‘Manage Add-ins’.
  • Now you must uncheck or clear the checkboxes against all the ‘Add-ins’ and then click on OK.
  • You now need to close Outlook Safe Mode and then just restart Outlook normally.

When you are done with the steps above then you should check if the error ‘0x800ccc78’ is resolved or not. If it is then you should enable one add-in at a time and also review Outlook for the error. If you see the error appearing right after activating a specific add-in then you should remove it immediately to resolve it.

Solution 8: Repair or Reinstall your Outlook

Here you could try and repair or reinstall Outlook to resolve the error 0x800ccc78. However, before then you would need to first back up your original PST file which you will find located in the following location.


The following are the steps to repair the MS Office:

  • You need to open the ‘Control Panel’ and click on ‘Programs’. Then under ‘Programs and Features’ you should click on the ‘Uninstall a program’ option.
  • Next, you will need to choose Microsoft Office from the given list and click on the ‘change’ button.
  • You now need to select the ‘Repair’ button and then follow the onscreen instructions to complete the repair process.
  • After the repair is completed you must reboot the system.
  • And now just open Outlook and check if the error ‘0x800ccc78’ has been resolved.

In case the solution doesn’t work then you should reinstall the program. To do so you must first uninstall MS Office and then install the latest build. After which you just need to sign in using your email account.

Solution 9: Create a New Outlook Profile

Now if your Outlook profile is corrupted then you can create a new Outlook profile and remove the old corrupt one. Follow the steps below;

  • You should close Outlook and then open the ‘Control Panel’.
  • Then click on the ‘User Accounts > Mail’.
  • After that, click on the ‘Show Profiles > Add’.
  • Next, type the name for the new profile and click on OK.
  • And then you must follow the onscreen prompts and configure your email under this new profile.
  • When once it is configured, you need to go back to the ‘Mail Setup’ window and choose your old profile.
  • And now you will have to click on the ‘Remove’ button and then click on ‘Yes’ to confirm.
  • After you have completed the above you will need to start Outlook.

In addition, Outlook will load your new profile and create a fresh Outlook data file (PST). After which it will download the mail items from the mailbox server. However, it would only download the latest emails or messages. Therefore to restore the old messages you would need to repair the PST file and then restore the mail items to the new profile.

Solution 10: Repairing the Outlook Data File (PST)

You should keep in mind that a corrupted Outlook PST file can also trigger the Outlook error 0x800ccc78. Nevertheless, you can also use a built-in ‘Inbox repair tool’ such as SCANPST.EXE to fix minor errors in the PST file. Follow the mentioned steps to do so;

  • You will need to first close Outlook and then open File Explorer.
  • After that, you should go to the following location and find the PST file.


  • Next, you will have to copy and backup the PST file to another folder or drive.
  • And then you just need to navigate to the following location;

C:\Program Files\Microsoft Office\root\Officexx

  • Remember that the path to the Office folder might vary based on the Outlook version and Windows edition.
  • You now need to double-click on the SCANPST.EXE program to run it.
  • Then you should click on the ‘Browse’ and select the PST file for repair after which you just need to click on the ‘Start’ button.
  • Now the tool will scan the PST file for errors and inconsistencies. It will also show you the errors and inconsistencies that are in the PST file if any.
  • When that is done you must click on the ‘Repair’ button to start the PST repair process. Now this process could take a while to complete.
  • At last, when the repair is done you just need to start Outlook.


When you are done following the above given step-by-step guide and instructions then you should definitely have the Outlook Error Code 0x800ccc78 resolved. However, if you come across any sort of glitches then you can always contact the technicians provided here. The team will then assist you in no time with the most suitable solutions.

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