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Outlook Express error guide

Summary: Having problems with Outlook Express? See if this error guide can help you.
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When Outlook Express fails to send or receive email it will usually tells you why on the error tab of the progress window (see figure1).

You can't always tell what's gone wrong from the message itself, instead you may need to refer to the error number that is given.

Image - Showing where the Error Number appears

Here's a list of the most common error messages with a short description of what they mean.

Click on the Error Number to see available information to help you fix the problem.

General Errors - Problems with the Outlook Express Application

Error Number Error Type Description
0x800CCC00 LOAD_SICILY_FAILED Authentication did not load
0x800CCC01 INVALID_CERT_CN Invalid certificate content
0x800CCC02 INVALID_CERT_DATE Invalid certificate date
0x800CCC03 ALREADY_CONNECTED User already connected
0x800CCC04 CONN N/A
0x800CCC05 NOT_CONNECTED Not connected to server
0x800CCC0A INCOMPLETE Message download incomplete
0x800CCC0B BUSY Server or incorrect domain on sender's email address
0x800CCC0D CANT_FIND_HOST Cannot locate server
0x800CCC0E FAILED_TO_CONNECT Cannot connect to server
0x800CCC0F CONNECTION_DROPPED Connection closed
0x800CCC10 INVALID_ADDRESS Address not known on server
0x800CCC11 INVALID_ADDRESS_LIST Mailing list not known on server
0x800CCC12 SOCKET_READ_ERROR Unable to send Winsock request
0x800CCC13 SOCKET_WRITE_ERROR Unable to read Winsock reply
0x800CCC14 SOCKET_INIT_ERROR Unable to initialise Winsock
0x800CCC15 SOCKET_CONNECT_ERROR Unable to open Windows Socket
0x800CCC16 INVALID_ACCOUNT User account not recognized
0x800CCC17 USER_CANCEL User canceled operation
0x800CCC18 SICILY_LOGON_FAILED Logon attempt failed
0x800CCC19 TIMEOUT Timeout
0x800CCC1A SECURE_CONNECT_FAILED Unable to connect using SSL

POP3 Errors - Problems receiving mail

Error Number Error Type Description
0x800420CB POP3_NO_STORE Mail cannot be stored on server
0x800CCC90 POP3_RESPONSE_ERROR Client response invalid
0x800CCC91 POP3_INVALID_USER_NAME Invalid user name or user not found
0x800CCC92 POP3_INVALID_PASSWORD Password not valid for account.
0x800CCC93 POP3_PARSE_FAILURE Unable to interpret response.
0x800CCC94 POP3_NEED_STAT STAT Command required.
0x800CCC95 POP3_NO_MESSAGES No messages on server.
0x800CCC96 POP3_NO_MARKED_MESSAGES No messages marked for retrieval.
0x800CCC97 POP3_POPID_OUT_OF_RANGE Message ID out of range.

SMTP Errors - Problems sending mail

Error Number Error Type Description
0x800CCC60 SMTP_RESPONSE_ERROR Invalid response.
0x800CCC61 SMTP_UNKNOWN_RESPONSE_CODE Unknown error code.
0x800CCC62 SMTP_500_SYNTAX_ERROR Syntax error returned.
0x800CCC63 SMTP_501_PARAM_SYNTAX Parameter syntax incorrect.
0x800CCC64 SMTP_502_COMMAND_NOTIMPL Command not implemented.
0x800CCC65 SMTP_503_COMMAND_SEQ Improper command sequence.
0x800CCC66 SMTP_504_COMMAND_PARAM_NOTIMPL Command not implemented.
0x800CCC67 SMTP_421_NOT_AVAILABLE Command not available.
0x800CCC68 SMTP_450_MAILBOX_BUSY Mailbox is locked and busy.
0x800CCC69 SMTP_550_MAILBOX_NOT_FOUND Mailbox not found.
0x800CCC6A SMTP_451_ERROR_PROCESSING Error processing request.
0x800CCC6B SMTP_551_USER_NOT_LOCAL User mailbox is known, but mailbox not on this server.
0x800CCC6C SMTP_452_NO_SYSTEM_STORAGE No space to store messages.
0x800CCC6D SMTP_552_STORAGE_OVERFLOW Storage limit exceeded.
0x800CCC6E SMTP_553_MAILBOX_NAME_SYNTAX Invalid mailbox name syntax.
0x800CCC6F SMTP_554_TRANSACT_FAILED Transaction failed.
0x800CCC78 SMTP_REJECTED_SENDER Unknown sender (incorrect e-mail address in the Reply-To field).
0x800CCC79 SMTP_REJECTED_RECIPIENTS Server rejected recipients.
0x800CCC7A SMTP_NO_SENDER No sender address specified.
0x800CCC7B SMTP_NO_RECIPIENTS No recipients specified.

NNTP Errors - USENET/Newsgroup Problems

Error Number Error Type Description
0x800CCCA0 NNTP_RESPONSE_ERROR News server response error.
0x800CCCA1 NNTP_NEWGROUPS_FAILED Newsgroup access failed.
0x800CCCA2 NNTP_LIST_FAILED LIST command to server failed.
0x800CCCA3 NNTP_LISTGROUP_FAILED Unable to display list.
0x800CCCA4 NNTP_GROUP_FAILED Unable to open group.
0x800CCCA5 NNTP_GROUP_NOTFOUND Group not on server.
0x800CCCA6 NNTP_ARTICLE_FAILED Message not on server.
0x800CCCA7 NNTP_HEAD_FAILED Message header not found.
0x800CCCA8 NNTP_BODY_FAILED Message body not found.
0x800CCCA9 NNTP_POST_FAILED Unable to post to server.
0x800CCCAA NNTP_NEXT_FAILED Unable to open next message.
0x800CCCAB NNTP_DATE_FAILED Unable to display date.
0x800CCCAC NNTP_HEADERS_FAILED Unable to display headers.
0x800CCCAD NNTP_XHDR_FAILED Unable to display MIME headers.
0x800CCCAE NNTP_INVALID_USERPASS Invalid user or password.

Errors - Problems using IMAP services

Error Number Error Type Description
0x800CCCD1 IMAP_LOGINFAILURE Login failed.
0x800CCCD2 IMAP_TAGGED_NO_RESPONSE Message tagged.
0x800CCCD3 IMAP_BAD_RESPONSE Invalid response to request.
0x800CCCD4 IMAP_SVR_SYNTAXERR Syntax error.
0x800CCCD6 IMAP_BUFFER_OVERFLOW Buffer limit exceeded.
0x800CCCD7 IMAP_RECVR_ERROR Recovery error.
0x800CCCD8 IMAP_INCOMPLETE_LINE Incomplete data.
0x800CCCD9 IMAP_CONNECTION_REFUSED Connection not allowed.
0x800CCCDB IMAP_CHANGEDUID User ID has changed.
0x800CCCDC IMAP_UIDORDER User ID command failed.
0x800CCCDD IMAP_UNSOLICITED_BYE Unexpected disconnect.
0x800CCCDE IMAP_IMPROPER_SVRSTATE Invalid server state.
0x800CCCDF IMAP_AUTH_NOT_POSSIBLE Unable to authorize client.
0x800CCCE0 IMAP_OUT_OF_AUTH_METHODS No more authorization types.

RAS/DUN Error - Problems communicating with dial-up/network system

Error Number Error Type Description
0x800CCCC2 RAS_NOT_INSTALLED RAS/DUN not installed.
0x800CCCC3 RAS_PROCS_NOT_FOUND RAS/DUN process not found.
0x800CCCC4 RAS_ERROR RAS/DUN error returned.
0x800CCCC5 RAS_INVALID_CONNECTOID Connectoid damaged or missing.
0x800CCCC6 RAS_GET_DIAL_PARAMS Error getting dial settings.

Winsock Errors - Problems encountered between Outlook Express and Operating system.

Error Number Error Type Description
0x800CCC40 WINSOCK_WSASYSNOTREADY Network subsystem is unusable.
0x800CCC41 WINSOCK_WSAVERNOTSUPPORTED Windows Sockets cannot support this application.
0x800CCC43 WINSOCK_WSAEFAULT Bad address.
0x800CCC44 WINSOCK_FAILED_WSASTARTUP Unable to load Windows Sockets.
0x800CCC45 WINSOCK_WSAEINPROGRESS Operation now in progress.
0x800CCC00 - Authentication did not load
  1. Reboot your computer and try again
  2. Check Service Status for mail problems
  3. Setup a new account in Outlook Express, re-entering your mail connection details. It is possible that your account has become corrupt


0x800CCC01 - Invalid certificate content / 0x800CCC02 - Invalid certificate date

The digitally signed email cannot be verified using the available digital certificate. Either the digital certificate is out-of-date or has been cancelled. Get your certificate re-issued by your certificate authority or try recreating your mail profile.


0x800CCC03 - User already connected

The mailserver believes that you are already logged into your mailbox:

  1. Close all connections on any machines that you connect to your email with and wait 20 minutes to check again
  2. If you are not logged in on another computer then someone may be using/downloading from your account, or something is wrong with your account
  3. If the problem continues, recreate your mail profile


0x800CCC05 - Not connected to server

Outlook Express can't talk to the mailserver.

  1. Check you are connected to the internet (view a webpage). If you are connected, double-check your mailserver address
  2. If you can't view webpages, re-connect and try again


0x800CCC0A - Incomplete
  1. This is a possible corruption of the file that records which emails you have downloaded. Close your internet connection and all programs. Search for the file 'pop3uid.dbx' and rename it to ''. Reconnect and try again
  2. If this doesn't work, reboot and try again
  3. It's possible that the error is being caused by an email waiting to be downloaded from the mail server. For POP3 mail try using webmail to view the contents of your mailbox. This may help identify the problem - if you see emails that you have already downloaded, try deleting them and the next in the list and try downloading using Outlook Express again. Your mail should then function properly


0x800CCC0B - Server busy or incorrect domain on sender's email address
  1. The mailserver may be slowing down because of heavy email traffic. Wait 5 minutes and try again
  2. If the problem continues check the service status page to see if there is a known problem with email service
  3. Check your email settings and make sure you are using the correct format for your email address


0x800CCC0D - Cannot locate server

Outlook Express can't see the mailserver.

  1. Check you are connected to the internet (by viewing a website with your web browser). If you are connected, double-check your mailserver address
  2. If you can't view webpages, re-connect and try again


0x800CCC0E - Cannot connect to server

Outlook Express can't talk to the mailserver.

  1. Check you are connected to the internet (by viewing a website with your web browser). If you are connected, double-check your mailserver address.
  2. If you can't view webpages, re-connect and try again


0x800CCC0F - Connection closed

Your modem/network was disconnected. If this happens often with dial-up there may be noise on your phone line or you may need updated modem drivers. With a network (broadband etc) the problem may be with your network hardware or drivers. Also check that any antivirus software you have installed is working correctly.


0x800CCC10 - Address not known on server

Outlook Express can't deliver an email because the address appears invalid. Check your spelling of the address (a common error is using a comma instead of a full stop in domain names) and try again. If there is one particular message causing a problem, delete it from your Outbox (or move it to your Drafts folder) and try again to verify this is the case.


0x800CCC11 - Mailing list not known on server

Outlook Express can't deliver to a mailing list, possibly because one of the email addresses isn't valid (check the spelling). Lots of mailing lists have restricted access, make sure that you are properly subscribed to the list.


0x800CCC12 / 0x800CCC13 / 0x800CCC14 / 0x800CCC15 - Winsock problems

This error usually means that a problem has occurred in your network protocols which is making it impossible for Outlook Express to transmit data over the network. A common fix is to re-install TCP/IP. First try rebooting your PC as this will often fix the problem.


0x800CCC16 - User account not recognized
  1. The most common cause for this is incorrect username and password details
  2. If they are not wrong, try setting up another identity with the same details. Sometimes accounts become corrupted. Creating a new copy of your email account can fix the problem


0x800CCC17 - User cancelled operation

This can occur if you cancel the sending and receiving of emails. Try rebooting your computer.
If this problem continues, the file 'pop3uidl.dbx' that logs which emails have been received may have become corrupt. You can do a search for the file and rename it '' then restart your computer.


0x800CCC18 - Logon attempt failed.

This simply means that Outlook Express was unable to log into your mail account.

  1. Check your account information (username, password and mailserver addresses)
  2. Make sure your account is still active (try and login to the portal and check your mail using the Webmail tool)


0x800CCC19 - Timeout

This error may be the result of a temporary glitch. Try rebooting your system and trying again. If this problem continues, the file' pop3uidl.dbx' that logs which emails have been received may have become corrupt. You can do a search for the file and rename it ''. Then reboot your system and try again.


0x800CCC1A - Unable to connect using SSL

This error indicates a problem connecting using the Secure Socket Layer. Remove this setting by editing your account settings and looking in the advanced tab.


General Errors- Applies to many of the errors on the above lists

Many errors can be fixed by rebooting your computer. Many problems are also caused by antivirus software not updating correctly. We recommend that you take a look at Microsoft's Knowledge Base regarding Outlook Express problems if your problems persist.


POP3 (Post Office Protocol 3) Errors

Problems that occur with POP3 affect the download of your emails. These problems occur, either because of a temporary glitch, file corruption, or because your account details are incorrect.

Checking your connection details are correct

Have you changed your account details recently? Make sure that you are not using CAPS LOCK while entering a case sensitive password. There is a quick way to check that you are using the right password and username, by connecting to the internet and using a program called a telnet client.

Telnet is program that allows you to access and talk to other computers, in this case you can pretend to be Outlook Express and talk directly to the mailserver. This will allow you to see if it's your email account or Outlook Express that is at fault.

  1. Click the Start button, then RUN
  2. In the RUN prompt, type 'cmd' (on Windows NT/2000/XP) or 'Command' on Windows 95/98/ME
  3. In the new window, type 'telnet 110' then press enter. Take care in your typing as you may not see what you type so its easy to make a mistake. If you do, it's best to start again
  4. You should be connected to the mailserver - you should see the response +OK Hello there which confirms the mailserver is OK
  5. Type in 'user your username' and hit the enter key (if your username was jsmith you would type 'user jsmith' )
  6. You will then get a message +OK Password required - type in 'pass your password' and press enter (If your password was opensesame you would type 'pass opensesame')

If it is correct, you will get an '+OK Well done' message. You are now in your mailbox and can be sure that your email account details are correct.


SMTP (Simple Mail Transfer Protocol) Errors

Problems that occur with SMTP affect your sending of emails. These problems can occur because of a temporary glitch (such as another program blocking port 25 which is used by Outlook express to send emails). It is possible that the outgoing mailserver address is wrong. This should be This is the first thing you should check.

Testing your access to port 25

You can check to see if your email is being blocked by using a telnet client. If you can connect to the outgoing mailserver on port 25, this will confirm that your problem mostly likely lies with the Outlook Express application, or your settings. To do the test:

  1. Click the Start button, then RUN
  2. In the RUN prompt, type 'cmd' (on Windows NT/2000/XP) or 'Command' on Windows 95/98/ME
  3. In the new window, type 'telnet 25' then press enter. Take care in your typing as you may not see what you type so its easy to make a mistake. If you do, its best to start again
  4. You should be connected to the mailserver - you should see a response that begins with "220." which confirms the port 25 is open. If you don't get the "220" response, either the mailserver is not operating properly (check service status), you're not connected to the internet or something on your system may be blocking port 25

If you run your own mailserver and don't limit access to it, our network engineers may have blocked your access to port 25. You will be contacted by support if this happens.


NNTP (Network News Transfer Protocol) Errors

NNTP allows Outlook Express to function as a USENET (newsgroup) client. Problems with NNTP will mean that you either cannot post to newsgroups or are unable to download the latest posts. In most cases problems will be as a result of incorrect settings or a corrupt news posting. You can check your settings by reading the guide to setting up Outlook Express for newsgroups. If there is a problem with USENET service, it will be indicated on the Service Status page.


IMAP (Internet Message Access Protocol) Errors

IMAP allows Outlook Express to store emails on the mailserver, allowing access to all your email, old and new from anywhere you can access email. Problems that occur with IMAP are mostly the same types of problems that occur with the more common POP3 mail system. If you were intentionally using the IMAP service, make sure that your settings are correct.

Because IMAP stores all your emails on the mailserver it is possible that a corrupt email (often with large attachments etc) may be the cause of problems. If you think this has occurred, raise a Question to our Support Team using the Help Assistant. Our network engineers will then investigate further.


RAS/DUN (Remote Access Server/ Dial-up Network) Errors

RAS/DUN errors indicate problems with your dial-up or network system. Outlook Express is tied to your dial-up settings, so if you open it, while not online, it can either automatically connect, or give you the option to connect. You should check your connection settings within Outlook Express
(Click Tools, Options, Connections, Change - to see your settings).


Winsock (Windows Socket/ Socket2) Errors

Winsock is the windows component that Outlook Express uses for all its TCP/IP (internet) communication. Winsock errors are usually caused by problems within the application/ operating system, sometimes as a result of bad configuration. They may be temporary in nature, vanishing on a reboot. They may be the result of a corruption within either Outlook Express or Windows.


More Help

Microsoft's Help and Support Centre has a lot of help for fixing Outlook Express problems. If you continue to have problems with Outlook Express, it's a good place to look for help.

You might also solve your problem by using the Help Assistant.


This page last updated 31st January 2012

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