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:

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:

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;

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;

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;

Solution 4: Disable the ‘Secure Password Authentication’

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;

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;

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;

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.

%localappdata%/Microsoft/Outlook

The following are the steps to repair the MS Office:

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;

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;

C:\Users\<YourUserNamer>\AppData\Local\Microsoft\Outlook

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

Conclusion

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.

Related Article: How do I Fix the Error Outlook.pst is not compatible?

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