How to Fix Outlook Error 0x800ccc78?

admin | Modified: 2020-10-16T13:04:11+05:30 | fix-error, How to, Outlook

MS Outlook is the most reliable email client application. But still, users have to face many issues while working with Outlook. One such error reported by users is when the Outlook application fails to send or receive a message and throws an Outlook error 0x800ccc78 code.

Due to this error users are not able to perform any function on the Outlook. So, in this article, we are going to discuss both the causes and resolutions for this issue.

Before we move to the resolution methods, let us first understand this Outlook mail error 0x800ccc78 in a detailed manner.

What is MS Outlook Error 0x800ccc78?

It is a sending reported error that occurs in Outlook while sending or receiving email messages. This is a complete error message “Unable to send the message. Please verify the e-mail address in your account properties. The server responded:550 is blacklisted.” Most of the time users get this error when their Outlook is not correctly configured to authenticate when sending emails.

Possible Causes For Outlook Error 0x800ccc78

Mainly there are two possible scenarios where you get this Outlook 2010 error 0x800ccc78.

Cause 1: The default port number in Outlook is up to 25 for transferring emails. When your Internet Service Provider blocked the port number 25 and changed it to 587, then you will get the Outlook error 0x800ccc78.

Resolution: Reset the Outgoing Port

In this case, you need to alter your port number to 587, follow the steps to do the same.

  1. Open Outlook.
  2. Go to Tools >> choose Account Settings.
  3. In the Account Settings window, click on Change.
  4. Click on the More Settings on Add New E-mail Account and Click on the Advanced tab.
  5. You will see Port numbers of IMAP and SMTP, Set the port number 587 for Outgoing Server (SMTP) and Click OK.
  6. Set the port number for the “Outgoing Server” to 587.

Cause 2: Another possibility of getting “Outlook sending error 0x800ccc78” is when the “My Outgoing Server (SMTP) Requires Authentication” is disabled.

Resolution: Check SMTP Server

To enable the SMTP server option, follow the below-mentioned steps:

  1. Open Outlook application.
  2. Click on Tools >>Account Settings.
  3. In the Account Settings window, click on the “Email” tab.
  4. Select “More Settings” from the lower-right corner.
  5. An Internet E-mail Settings window will open, check the box labeled: “My outgoing server (SMTP) requires authentication.”
  6. Select the radio button “Use same settings as my incoming mail server”.
  7. At last, restart your Outlook application and check whether your Outlook is working properly or not.

Although, the manual solutions are free to use they didn’t resolve the Outlook error 0x800ccc78 caused due to corrupt PST files. So, in the next section, we are going to discuss the automated tool that can resolve the error by repairing broken PST files.

Automated Solution to Resolve Outlook Sending Error 0x800ccc78

Outlook recovery utility is specially designed in a well structure manner to repair highly corrupt files. The utility is able to restore the data from corrupt PST files in PDF, EML, MSG, HTML format. This tool is enough capable to repair the file, resolve all issues, and make it accessible in Outlook.


In this blog, we have explained two possible reasons for getting Outlook error 0x800ccc78 while sending email in Outlook. Depending upon its causes we have mentioned the resolution methods to fix the Outlook error. The manual methods failed to resolve the issues if it caused due to corrupt PST files. For that case, we have recommended an automated tool that will quickly repair the broken files without any hassle.