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