Email errors can be looked up by the error code that is shown at end of an email error message. The code can be used to identify the cause of the problem. Common ways to resolve the error are listed by the error code. The most common error codes are caused by a username, password, or mail server address most cases, the solution for Outlook errors are relatively simple, however, additional work on the PC may be needed to resolve the issue.

Solutions For Common Errors

More in depth information about all Microsoft Email Error Codes can be found at the link below:
Microsoft Outlook & Outlook Express Error Codes list

Error:  0x800CCC91: POP3 Username Invalid

Symptom
There was a problem logging onto your mail server. Your UserName was rejected. Account: 'domain name', Server: 'pop3.norton.antivirus', Protocol: POP3, Server Response: '-ERR', Port: 110, Secure(SSL): No, Server Error:   0x800CCC90

Solution
This error message is caused by the fact that an anti-virus program, in this case Norton AntiVirus,  has been set to scan all emails automatically. Changing the settings within Outlook/Outlook Express will not solve the issue. To try to resolve this issue, it will be necessary to change the settings in the virus protection software. For assistance with this, please contact the product vendor of the anti-virus program.

Error: 0x800CCC92: POP3 Password Invalid

Symptom
There was a problem logging onto your mail server. Your Password was rejected.'domain name', Server: 'domain name', Protocol: POP3, Server Response: '-ERR invalid user or password', Port: 110, Secure(SSL): No, Server Error: 0x800CCC90, Error Number: 0x800CCC92

Solution
Check the Outlook/Outlook Express account settings, making sure that the POP3 and SMTP servers are correct, and that the full email address is in the username field and password are correct. If the program is still displaying that error message, it could be that the password has become corrupted. Please contact the ISP's technical support to have it reset.

Error: 0x800CCC7D: Server does not support SSL

Symptom
The server does not support a SSL connection. Account; domain name' Protocol SMTP, server response '250 HELP' Port; 25, Secure (SSL) Yes, Server Error 250, error number 0x800CCC7D.

Solution
This problem happens because the version of Outlook Express is set up to use Secure Socket Layer (SSL), which the email server may not use. To fix this problem follow the instructions below:

1. Open Outlook Express.
2. Click on Tools at the top of Outlook Express.
3. Inside the box, select Accounts.
4. Highlight the email account from the options and click Properties on the right-hand side of the box.
5. Then click the Advanced tab inside the Account Properties.
6. On this screen remove the checks from the boxes This server requires a secure connection under both Outgoing mail (SMTP) and Incoming mail (POP3).
7. Click Apply then OK at the bottom of the page to save the settings and return to the Accounts box.
8. Click Close to return to the Outlook Express main screen.

The email account should now be able to send and receive properly. If the program is still displaying the same error, follow the instructions again to make sure the settings were saved. If that does not resolve the issue, please contact the ISP's technical support.

Error: 0x800420CB: Message could not be opened

Symptom
Message Could Not Be Opened From Outbox Folder, Account: "account name" MailAccount, Server: 'outgoing mail server name', Protocol:SMTP,PORT:25,Secure(SSL):NO, Error Number:0x800420CB

Solution
The usual cause of this problem is an Outbox..dbx file which has become corrupted. To try to fix this problem follow the instructions below:

1. Open Outlook Express
2. Once Outlook Express is open, click on Tools at the top of the program
3. Inside the box that opens, select Accounts from the list
4. An Internet Accounts box will open, click on the Mail tab inside of it
5. If there are duplicate copies of the same email account, click on the extra account, and then click Remove. Keep doing this until all duplicated accounts have been removed
6. After removing all duplicate accounts, only one copy of the account should be left  Click the Close button on the right-hand side of the box to return to the main screen

Still having problems with this error message? Try renaming the Outbox.dbx file, although this will permanently delete any messages still in the Outbox.  If there are any messages in that outbox that need to be saved, please save the emails to the Drafts folder first.  To rename the Outbox.dbx file follow the instructions below:

1. Right-click the Start button on the PC's desktop
2. click Find or Search
3. Search for the Outbox.dbx file
4. Right-click the file, click Delete, and then click Yes
5. Start Outlook Express, and see if that resolves the issue.

If the program is still displaying the same error message after trying those instructions, a trained PC technician might be needed to take a look at the program, incase it needs to be reinstalled.

Error: 0x800420CD: One of recipients addresses rejected by the server

Symptom
Cannot send message as one of recipients addresses rejected by the server.

Solution
Note:Before attempting any of the following steps, make sure that any existing messages are removed from the Outbox first.

1. If the address is being supplied by the address book, and not being typed in manually, try typing the entire address in manually. Sometimes data in the address book can become corrupted. If this resolves the issue, remove and recreate the account in your address book.
2. Check the email address being sent to verify that it is correct. Check for spelling, extra spaces or characters and then try again.
3. Attempt to send a message to yourself. If the same error is displayed, it could indicate a problem sending mail to everyone.
4. Disable any firewall or virus protection which may be running and try again.
5. If the program is still having a problem, please call the ISP's technical support. 
   

Error: 0x800CCC0D: The host could not be found

Symptom:
The host [your ISP] could not be found. Please verify that you have entered the server name correctly. Account '[name]', Server, '[your ISP]', Protocol: ',Port ', Secure(SSL): No Socket Error: 11001, Error Number: 0x800CCC0D.

Solution:
This error indicates that the server information may not be correct in the mail program. Please check the "Incoming" and "Outgoing" mail servers. Verify that there are no spaces, extra spaces or characters. 

If the information is correct, and the program still cannot check for mail, tryiing checking the internet and make sure there is an active Internet connection. This error also appears when the internet is down.  If a connection to the Internet is available, and the program will still not connect to the mail server, try restarting the computer. If that also fails to resolve issue, please contact the ISP's technical support.

Error:  800CCC0131: MSIMN Errors

Symptom
When starting Outlook/Outlook Express or trying to send an email message, one of the following error messages might appear:

• MSIMN caused an invalid page fault in module Msoe.dll
• MSIMN caused an invalid page fault in module "unknown"
• MSIMN caused an invalid page fault in module Directdb.dll
• MSIMN caused an exception C0000006H in module Directdb.dll
• Outlook Express: The message could not be sent. There is not enough Disk space.
• Unknown error has occurred. Protocol: SMTP Port: 0 Secure: No [SSL] Error: 0x800C0131

Solution
The usual cause of this error is a missing or damaged folders.dbx file. Either that or it is using a read only attribute. To fix this bug:

1. Click Start on the desktop
2. Select Find or Search in the menu
3. Click the option to search in Files or Folders
4. In the File Name field, type folders.dbx
5. In the Look In field, click the main hard disk (this is usually drive C:), and then click Find Now
6. Find and right-click the Folders.dbx file, and then click Rename
7. Change the file name to folders.old, and click OK
8. Start Outlook Express again. This creates a new Folders.dbx file automatically 
   

Error:  Kernel Errors - Messages involving kernel32.dll

Symptom
If running Windows 95 or 98 and trying to start Internet Explorer or Outlook/Outlook Express, the PC may hang, and one of the following error messages might appear:

• Explorer caused an invalid page fault in module Kernel32.dll.
• Commgr32 caused an invalid page fault in module Kernel32.dll.
• Mprexe caused an invalid page fault in module Kernel32.dll.
• Msgsrv32 caused an invalid page fault in module Kernel32.dll.
• Iexplore caused an invalid page fault in module Kernel32.dll.

Solution
The cause of this message is a damaged password list file (.pwl). To fix it:

1. Click Start and in the menu select Find or Search.
2. Inside the box that opens, click search in Files or Folders.
3. In the File Name box, type *.pwl, and then click Find Now.
4. In the list of found files, right-click each file, and then click Delete. Repeat this step until all of the .pwl files are deleted.
5. On the File menu at the top, click Close.
6. Restart the computer. The password list files are re-created automatically when a user logs on to Windows. 
   Note: If running an earlier versions of Windows 95, it might be needed to download the Mspwlupd.exe file from the Microsoft web site, and then double-click the file to run it. 
   

Error:  Wininet Errors - Messages involving wininet.dll

Symptom
When using Outlook Express, if an error messages is displayed involving wininet.dll, for example, MSIMN has caused an invalid page fault in module.

Solution
There are several potential causes of this error, all detailed on the Microsoft Knowledge Base.