Outlook Error 0x8004210E when trying to receive mail

I get the following error message when I try to receive mail using Outlook: Task 'Mailbox Name - Receiving' reported error (0x8004210E) : 'Your mailbox is temporarily unavailable because another e-mail message is being delivered to it or another mail application is accessing it. The server responded: -File busy try again later! or -ERR Unable to lock mailbox'

Solution

Under certain conditions (eg. network problems, malformed email messages, more than one email client being configured to poll the server) the lock file which is used to stop more than one person logging into the account at once, fails to be deleted at the end of the pop3 session.

It then prevents you from logging in again, generating the Outlook error above.

If you are experiencing this problem contact Kalkadoon Corporate Solutions via your control panel and we will remove the lock file from your account.

If the problem occurs again, please make sure that you don't have more than one email client configured to check the same account.

This error can also occur if the message being downloading is malformed, and the client computer has anti-virus or anti-spam software running (such as McAfee or Norton’s Anti-virus). The software installed on the client has problems with interpreting the email and doesn't finish, and doesn't try to download the next message from the server.

To resolve, the anti-spam or anti-virus software has to be disabled if not at least to diagnose and debug. In some cases a single message could be holding up the download on the client firewall end, once this message is removed or let through by disabling as previously mentioned every thing can be resumed as per the previous configuration settings.

It is also recommended that you enable server-side Anti-Spam and Anti-Virus on your email accounts via your web control panel. This will prevent most malformed emails from reaching your inbox in the first place.