Microsoft Outlook (and Outlook Express) often displays cryptic error codes (usually hexadecimal numbers like 0x800CCC**) when something goes wrong with sending or receiving email. These error codes are usually accompanied by an error message describing the problem. Below, we outline some common Outlook error codes, explain their typical causes, and provide solutions to resolve them. Each error is grouped by category (sending issues, receiving/authentication issues, and connectivity issues) for clarity.
These errors occur when Outlook is unable to send outgoing mail via the SMTP server. Causes range from authentication problems to port blocking. Common sending-related error codes include:
0x800CCC65: This error indicates that a firewall or antivirus is blocking Outlook’s outgoing connection to the mail server. The SMTP request never reaches the server.
Solution: Temporarily disable any local firewall/antivirus (e.g. ZoneAlarm, Norton, McAfee) and try again. If sending works with it off, adjust the software’s settings to allow Outlook outbound email access.
0x800CCC67: This error typically means that the SMTP connection is being blocked or misconfigured. This often happens if your ISP blocks the default SMTP port or if security software interferes.
Solution: Try changing the SMTP port from the default 25 to an alternate port (such as 26 or 587) . Also ensure your SMTP server settings (server name, encryption) are correct and disable any firewall/AV temporarily to test.
0x800CCC69: This error appears with a server response like “550 External MTA’s must be authenticated” when sending without proper SMTP authentication. In other words, the mail server rejected the message as an unauthorized relay.
Solution: Enable authentication for the outgoing mail server in your Outlook account settings. In Outlook, check “My outgoing (SMTP) server requires authentication” and use the same login credentials as your incoming mail.
0x800CCC78: This error means that the sender's address is invalid or in an invalid format. Outlook/Outlook Express requires the sender's login to be the full email address, not just a username. If it’s just “user” instead of “[email protected]”, the send will fail. Solution: Update your account settings so that the Email Address and User Name fields contain your full email address (e.g. username@mydomain.com) .
0x800CCC79: This error indicates a relay problem due to missing SMTP authentication or improper order of operations. Some email providers require you to “authenticate SMTP before POP,” meaning you must log in (or check mail) before sending, or simply have SMTP auth turned on.
Solution: Ensure that your client is configured to authenticate with the SMTP server. In practice, checking “Outgoing server requires authentication” (and possibly performing a send/receive after login) resolves this.
0x800CCC0B: This is a general send/receive error (“unknown error occurred”) often related to SMTP. This can occur if the SMTP settings are incorrect or connectivity is disrupted, causing Outlook to time out or give up on sending.
Solution: Verify that your SMTP server settings (server name, port, SSL, auth) are correct. If the issue persists, use the troubleshooting steps below (restart Outlook, try alternate port 26 or 587, disable firewall/AV, etc.) . This error is usually resolved by one of the common fixes in the last section.
0x8004210B: This error means “the operation timed out waiting for a response from the sending (SMTP) server.” In some cases it can also be triggered by an invalid email address in a distribution list, which causes the send to stall.
Solution: Double-check that all recipient addresses are valid (especially in group emails). Also, increase the server timeout setting in Outlook (under account advanced settings) in case the mail server is slow to respond. If timeouts persist, consider the possibility of firewall interference or try using your ISP’s SMTP server as a relay.
These errors occur when Outlook fails to log in to the incoming mail server (POP3/IMAP) or fetch messages. Causes include incorrect credentials or misconfiguration:
0x800CCC92: This error means your email login was rejected by the server (POP3/IMAP authentication failed) . The server responds with “-ERR Login failed” or similar. Common causes are an incorrect password or not using the full email address as the username.
Solution: Verify that your email address and password are entered correctly. Often, the username should be the full email (e.g. user@domain.com, not just the user) . If the credentials are correct but it still fails, your mailbox could be locked or corrupted – try resetting the email account password, and if using cPanel webmail, consider removing and re-adding the account .
0x800CCC18: This error is related to Secure Password Authentication (SPA). This occurs when Outlook is set to use SPA but the mail server does not support it, resulting in a login failure with “Invalid command” from the server . Solution: Disable the Secure Password Authentication in your account settings. Most standard ISP/hosted mail servers use plain login or SSL without SPA, so ensure the SPA option is unchecked unless your provider specifically requires it.
0x800C0133: This error is specific to Outlook Express and indicates a corrupted mailbox store (DBX file), often the Inbox folder (for example, due to the file exceeding its size limit or becoming damaged). When this happens, you may be unable to download new messages.
Solution: One common fix is to move or rename the Inbox.dbx file (for Outlook Express) to force the client to create a new mail store. Essentially, you need to repair or reset the local mail storage. Microsoft newsgroup discussions note that disabling antivirus email scanning can also help prevent this issue.
0x8004210A: This error means “the operation timed out waiting for a response from the receiving (POP) server.” It’s a timeout on incoming mail. This can occur if the mail server is slow or if you have a very large message blocking the retrieval.
Solution: Increase the server timeout setting for the account in Outlook . You can also log into webmail to delete any suspicious large emails that might be hanging up the process. Ensure that your internet connection is stable as well. In some cases, antivirus email scanners can cause timeouts – try disabling email scanning if timeouts continue.
These errors indicate that Outlook cannot reach the mail server at all, often due to network or configuration issues such as incorrect server names or ports, or blocked connections:
0x800CCC0D: This error means “cannot find server.” Outlook is unable to resolve your mail server’s address (e.g. mail.domain.com). Causes include a misspelled server name, a DNS issue, or the server being unreachable.
Solution: Verify that the email server (POP/IMAP/SMTP) names in your account settings are correct. Make sure you have an internet connection and that the domain is active. If the domain name still cannot be resolved, you can try using the server’s IP address temporarily . Also check that no local firewall or network policy is blocking Outlook.
0x800CCC0E: This error indicates “cannot connect to server – connection failed.” It often comes with a socket error 10061, meaning the connection was refused. Common reasons are incorrect port numbers or ISP port blocking. For example, using a non-existent port (such as 255 or 1100 by mistake) will trigger this error. It can also happen if your ISP blocks port 25 (SMTP).
Solution: Check your port settings – the default ports are 110 for POP3, 143 for IMAP, 25 (or 587) for SMTP without SSL, and 995 (POP3), 993 (IMAP), 465 or 587 (SMTP) when encryption is used. Correct any wrong port (e.g. Use 110 instead of 1100 for POP, or 25/587 instead of 255) for SMTP. If the ports are correct, ask your ISP if they block any email ports – you may need to use an alternate SMTP port (26 or 587) .
0x800CCC0F: This error means “the connection to the server was interrupted” or “server unexpectedly terminated the connection.” It can occur if the session is dropped due to network issues or if using the wrong security settings. One common scenario is enabling SSL for incoming mail but leaving the port at 110/143 instead of the SSL port – this mismatch causes the connection to fail immediately. Another cause can be security software scanning or blocking the connection.
Solution: Ensure that if you enable SSL for POP/IMAP, you also change the port to 995/993 respectively (and for SMTP SSL, use port 465 or appropriate) . If the error persists, temporarily disable antivirus/firewall software (since some have been known to cut off email connections). Also, if you have a very large email or attachment being downloaded, it could trigger a timeout – deleting that email via webmail could help.
0x800CCC19: This error is a timeout error for a POP operation, often attributed to antivirus interference. According to Microsoft’s documentation, it’s associated with a client-side issue where a security program might be interrupting the connection.
Solution: Increase the server timeout in Outlook settings and try again. If it still occurs, disable any email scanning features in your antivirus software (as some virus scanners proxy the connection and can cause delays). Also ensure you don’t have unusually large emails stuck in the queue.
IMAP Root Folder Error: In some IMAP configurations, especially with cPanel-hosted email, you might see an error like “Your specified root folder path ‘public_html’ could not be found. Please verify that your root folder path is correct.” . This is not a numbered error code but a configuration mistake. This occurs if you set the IMAP root folder path incorrectly (e.g. trying to use public_html or another directory).
Solution: Leave the “Root folder path” setting blank for IMAP accounts unless instructed otherwise. Outlook will automatically detect the correct folder structure. An incorrect root path can prevent you from seeing your mail folders.
If you are still encountering Outlook errors, consider these general fixes that often resolve common email issues :
Restart Outlook/Computer: Fully close Outlook and restart your computer. This can clear stuck connections or processes and often fixes transient errors.
Verify Account Credentials: Ensure you have the complete email address entered as your username and the correct password. Typos or using just the part before @ can cause authentication errors.
Check Mail Server Names: Your POP3/IMAP and SMTP server addresses are usually of the form mail.your-domain-name.com. Make sure they are typed correctly (no typos) and that your DNS has propagated if it’s a new domain.
Enable SMTP Authentication: In your account settings, make sure “Outgoing server (SMTP) requires authentication” is enabled. Use the same login details as for incoming mail, unless your provider specifies different credentials for SMTP.
Change SMTP Port if Needed: If you suspect your ISP blocks port 25 (common for residential ISPs to curb spam), switch the SMTP port to 26 or 587 (whichever your mail provider supports) . Port 587 is the modern standard for authenticated SMTP submission. Also ensure that the encryption setting (SSL/TLS) matches the port.
Temporarily Disable Firewall/AV Software: Security programs can mistakenly block email ports or alter traffic. Turn off your firewall/antivirus briefly to see if sending/receiving works. If it does, you may need to adjust your software’s settings to allow Outlook and email traffic. - Do not turn protection off; instead, configure exceptions for Outlook or the mail ports.
Try Your ISP’s SMTP Server: If you still cannot send via your usual SMTP server, you can attempt to use your Internet Service Provider’s outgoing mail server as a relay. This often requires using your ISP email credentials. For example, many ISPs provide an SMTP server like smtp.yourISP.com that you can use when on their network.
By systematically checking the above points, you can resolve the majority of Outlook send/receive errors. In summary, Outlook error codes may look intimidating, but they usually point to straightforward issues like incorrect settings, authentication requirements, or network blocks. With the appropriate adjustments – correcting server names, enabling authentication, using the right ports, and adjusting security software – your email should start flowing again .
Add Comment