0x800CCC90 POP3 RESPONSE ERROR – Client response invalid

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Outlook Express is a swift, responsive email application, perfect for efficient communication. It supports multiple accounts and offers a well-organized mailbox. Occasionally, errors disrupt its functionality, like the one in POP-based accounts:

0x800CCC90 POP3 RESPONSE ERROR – Client response invalid

If the POP Server doesn’t establish a valid connection with Outlook Express, it fails to process the request, leading to the display of an error.

Preceding error message is generated due to following reasons:

The issue arises because the Windows Firewall is enabled, causing connectivity problems between Outlook Express and the mail server. Additionally, your antivirus software is configured to automatically scan emails during the send/receive process.

You can resolve the issue by following below given measures:

• Turn Off Firewall: While the firewall is a critical security feature designed to safeguard your computer against unauthorized access, it can occasionally interfere with Outlook Express’s connection to the mail server. To check if the firewall is causing the issue, temporarily disable it. Here are the steps to turn off the firewall:

1. Open Control Panel through Windows Start Menu.
2. Double-click Windows Firewall icon. Windows Firewall screen appears.
3. Click Off (not recommended) option.
4. Click OK.

After disabling the firewall, continue using Outlook Express. If the issue is resolved, you can choose to either keep the firewall off or turn it back on. However, if the problem persists, proceed to the next solution.

• Modify Anti-virus Settings: If you have set up your antivirus to scan incoming and outgoing emails automatically, it can occasionally cause issues with email processing in Outlook Express. To address this, it’s advisable to adjust your antivirus settings to disable automatic email scanning. After making these adjustments, remember to restart your antivirus software.

The solutions mentioned above will assist you in resolving the “0x800CCC90 POP3 RESPONSE ERROR – Client response invalid” error message.

Looking for DBX Repair Solution?

When the DBX file becomes corrupt, it may fail to establish a connection with the POP Server, leading to an error. To recover the mailbox content, consider using Kernel for Outlook Express recovery software, which can extract each file from the DBX format and save it as EML or DBX files. A free trial version of the software is also available for limited recovery needs.