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“An unknown error has occurred” is not one Windows Live Mail problem with one universal fix. It is a generic failure message that can appear while opening or deleting mail, receiving through POP3 or IMAP, or sending through SMTP. The numeric error ID, the action that triggered it, and whether webmail still works determine the safest solution. Back up messages and contacts first, then test webmail, verify the account’s current server settings, inspect the Outbox, and only afterward consider the code-specific index rebuild or a Windows Essentials repair.
What does “An unknown error has occurred” mean in Windows Live Mail?
The wording is a wrapper, not a diagnosis. Microsoft Q&A cases show the same sentence attached to message deletion, message opening, POP3 downloads and SMTP sending. Those workflows use different local files, account settings and server operations, so applying a single “fix” to every case can make the situation worse.
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Windows Live Mail often displays a more useful error ID in the same dialog or in the error details. Record that code exactly, including zeroes and letters, before closing the window. Also note what you were doing, the account protocol, server names, port numbers and TLS/SSL choice. For example, a failure to download mail with 0x800C013E points toward a different investigation than a send failure with 0x8007007A.
Which error code and action are you seeing?
Use the code and the failed action to choose a branch rather than treating every unknown error alike.
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| Error ID or symptom | Where it commonly appears | Most relevant first check |
|---|---|---|
0x800C013E |
POP3 or IMAP receiving; sometimes associated with damaged local indexes | Back up the mailbox, then rebuild the Windows Live Mail folder, stream and UIDL indexes |
0x80004005 |
Generic POP3 failure, sometimes tied to a problematic message on the server | Open webmail and move or delete the message that cannot be processed |
0x8007007A |
Sending; a message can remain stuck in the Outbox | Remove or recreate the stuck message, particularly if the problem began after an old photo-sharing workflow |
| No code shown | Opening, deleting, receiving or sending | Capture the action, test webmail and inspect account properties before changing files or the registry |
These associations are clues, not guarantees. A provider change, damaged installation or an authentication mismatch can produce a similarly vague dialog with a different number.
How should I troubleshoot Windows Live Mail without losing messages?
Preserve the local archive before registry editing, repair, removal or reinstallation. A USB flash drive for email backup is useful preparation for repair or migration, but it does not fix the error itself.
- Back up mail and contacts. Export messages and contacts using the available Windows Live Mail export tools, and copy any local mail folders to another drive. Keep the backup disconnected or otherwise protected while troubleshooting so an accidental cleanup cannot remove both copies.
- Write down the context. Record whether the failure happens when opening, deleting, receiving or sending. Capture the complete numeric ID and the account’s incoming and outgoing server, protocol, port and encryption settings.
- Try the provider’s webmail. Sign in through a browser and open, send and receive a test message. If webmail works, the mailbox and credentials are probably usable and the fault is more likely local configuration, indexes or client compatibility. If webmail also fails, resolve the mailbox or provider problem before modifying Windows Live Mail.
- Check for a server-side message problem. In webmail, look for an unusually large, malformed or recently imported message. Move it to another folder or delete it only after confirming that it is not needed; a POP3 client may repeatedly fail on one item and never reach later messages.
- Inspect the Outbox. A malformed attachment or obsolete sharing message can block every later send. Save any needed text or attachments, then delete the stuck item and compose a fresh message.
- Compare account properties with current provider documentation. Verify the incoming protocol (POP3 or IMAP), incoming and outgoing host names, ports, TLS/SSL requirement, username format and password. Do not copy settings from another account or rely on an old setup guide.
- Apply a code-specific repair only after those checks. The index rebuild for
0x800C013Eis appropriate only when the symptom and code fit. Use Windows Essentials repair before considering removal and reinstall.
How do I tell whether the problem is Windows Live Mail or the mail server?
Webmail is the quickest dividing test. A browser session reaches the provider without using Windows Live Mail’s local database, indexes or stored protocol settings.
When webmail works
Successful sign-in and normal message activity make a bad password or a total provider outage less likely. Concentrate on the client: verify its account properties, clear a blocked Outbox item, and investigate local index or installation damage. This does not prove that every server setting is correct; an old client can still fail when the provider requires authentication or TLS behavior it cannot supply.
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When webmail fails too
Do not start with registry edits. A locked account, changed password, provider outage, quota issue or troublesome server message can affect both interfaces. Use the provider’s recovery and support process, and resolve or move the offending message in webmail before testing the desktop client again.
How do I fix error 0x800C013E by rebuilding Windows Live Mail indexes?
For a POP3 or IMAP failure associated with damaged local indexes, close Windows Live Mail and create three DWORD values under the exact registry key HKEY_CURRENT_USERSOFTWAREMicrosoftWindows Live Mail. Set each value’s data to 1, then restart the program. Back up your mail first and use the exact names; an incorrect registry edit can damage Windows or change unrelated settings.
- Close Windows Live Mail. Check Task Manager if necessary to ensure the program is no longer running.
- Open Registry Editor by pressing
Win+R, enteringregedit, and accepting the User Account Control prompt. - Navigate to
HKEY_CURRENT_USERSOFTWAREMicrosoftWindows Live Mail. Do not create the values under a similarly named key or under another user account. - Create a new DWORD (32-bit) Value named
RecreateFolderIndexand set its value data to1. - Create another DWORD named
RecreateStreamIndexand set it to1. - Create a third DWORD named
RecreateUIDLIndexand set it to1. - Close Registry Editor and start Windows Live Mail. Allow time for the indexes to be rebuilt, then test the affected account.
This procedure rebuilds indexes; it is not a method for recovering mail that has already been deleted. If the error remains, remove the temporary values only if your troubleshooting instructions require it, and move to account-setting verification or installation repair rather than repeatedly changing unrelated registry entries.
What should I do when Windows Live Mail cannot send because the Outbox is stuck?
A message that never leaves the Outbox can prevent later messages from being submitted. Microsoft Q&A documents error 0x8007007A after an obsolete OneDrive photo-album share left such a message behind.
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Safe Outbox cleanup
- Open the Outbox and identify the oldest message or the one with a large attachment or expired sharing link.
- If its contents matter, copy the text and save the attachments outside Windows Live Mail.
- Delete the stuck item, or recreate it as a new message without the obsolete attachment or share.
- Send a small test message to yourself. If it succeeds, address the original message separately rather than sending it repeatedly.
If Windows Live Mail immediately recreates the message, close the program, restart Windows, and check the Outbox again. Persistent failures after cleanup usually require checking SMTP host, port, authentication and TLS settings, or testing the account in webmail.
How do I repair or reinstall Windows Live Mail?
Repair is safer than a clean removal because it attempts to correct the installation while preserving the data you have backed up. Microsoft support guidance recommends backing up mail and contacts, using the Windows Essentials repair option, and treating clean removal and reinstallation as later steps.
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Run the Windows Essentials repair option
- Close Windows Live Mail and any other Windows Essentials program.
- Open Control Panel, choose Programs and Features, select Windows Essentials, and choose Uninstall/Change (the wording can vary by Windows version).
- Select the option to Repair all Windows Essentials programs and let the process finish.
- Restart Windows, open Windows Live Mail and test the same action that produced the error.
When clean removal is justified
Use removal and reinstall only when repair fails and your local mail, contacts, account details and exported files are safely preserved. A clean removal can remove configuration and registry data, so it may leave you needing to recreate accounts and re-import an archive. Do not assume an unofficial installer is a current Microsoft release: Microsoft states that Windows Essentials 2012 became unsupported on Windows 10 on January 10, 2017, and is unavailable for download.
Can Windows Live Mail still connect to modern mail services?
It may continue to work with some providers and settings, but it is an unsupported client. Microsoft’s support information gives January 10, 2017 as the end of support for Windows Essentials 2012 on Windows 10. A Microsoft moderator also warns that some connections from the earlier-generation client may no longer work as expected and points users toward webmail or Outlook for Windows.
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A successful repair therefore means only that the old installation is functioning again; it does not guarantee compatibility with a provider’s future authentication or TLS requirements. Decide whether to keep using it by comparing the practical trade-offs:
| Option | Local archive | Modern authentication and TLS | Import/export | Security maintenance | Setup effort |
|---|---|---|---|---|---|
| Continue with Windows Live Mail | Familiar local folders can be retained if backed up | May fail when a provider changes requirements | Existing Windows Live Mail data remains convenient to access | Unsupported | Lowest if the current installation still works |
| Provider webmail | Local archive requires export or separate backup | Handled by the provider’s current web service | Depends on the provider’s export tools | Maintained by the provider | Low; sign in through a browser |
| Supported desktop mail client | Usually supports importing an exported archive, but check before migrating | More likely to support current requirements | Varies by application and mailbox format | Receives updates from its vendor | Moderate; accounts and local data must be configured |
Keep at least one readable backup of the archive before migration. If the account works in webmail but the old client repeatedly fails, moving to a supported option reduces dependence on an unmaintained program.
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Clear out junk files and repair common Windows errorsFree Scan →Fix the driver behind crashes, sound loss and screen glitchesFind Drivers →What mistakes should I avoid?
- Do not treat the sentence as a single diagnosis. The same wording covers unrelated open, delete, receive and send failures.
- Do not edit the registry before backing up. The index values are a targeted workaround, not a general repair command.
- Do not promise recovered mail. Rebuilding indexes cannot restore messages already deleted from the local store or server.
- Do not blame one Windows update or one server setting without evidence. The documented cases involve multiple error IDs and protocols.
- Do not download Windows Essentials from an unofficial site as if it were a supported Microsoft product. Microsoft says the suite is unavailable for download.
- Do not repeatedly retry a blocked Outbox message. Remove or recreate the item so it cannot hold every later message in the queue.
What is the most reliable path when none of the fixes works?
Stop changing the client once you have preserved the archive, confirmed the account in webmail, checked current server settings, cleared the Outbox and tried the appropriate repair. At that point, the remaining issue is likely provider-side compatibility or a failure that an unsupported application cannot resolve. Use webmail or migrate to a maintained desktop client while keeping the exported messages and contacts available for reference.
Frequently Asked Questions
Will reinstalling Windows Live Mail delete my old emails?
It can remove local configuration and make the existing folders harder to find, even if every message is still present on disk. Export or copy the messages and contacts before uninstalling, and verify that the backup opens or can be imported on another system.
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Why does Windows Live Mail download the same messages repeatedly?
A damaged POP3 UIDL index can make the client lose track of which messages it has already retrieved. The RecreateUIDLIndex value is part of the targeted rebuild for the documented 0x800C013E case, but repeated downloads can also result from provider-side message handling.
Can changing the email password fix an unknown error?
Only when the stored password is actually wrong or the provider recently changed its authentication rules. Test the credentials in webmail first; if browser access works, compare the client’s username format, port and encryption settings instead of changing a working password again.
Do these 3 things before closing this tab:
1Repair Windows errors before they cause bigger problems2Scan for outdated or missing drivers - takes under a minute3Clear out junk files and repair common Windows errorsIs Windows Live Mail available for download from Microsoft today?
Microsoft says Windows Essentials 2012 has been unsupported on Windows 10 since January 10, 2017 and is unavailable for download. Avoid treating third-party installers as an official, maintained replacement.
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