"An unknown error has occurred" error message in Outlook

As you follow the steps to resolve the problem, you are asked to use a file that is typically a hidden file. So that you can find that file when you want it, you must configure Windows Explorer to show the hidden files on your computer. To do this, follow these steps:

Show hidden files in Windows 7

1. Click Start
   , type Folder Options in the Start Search box, and then press Enter.
2. Click the View tab. The screen shot for this step is listed below.
   
   
3. Under Advanced Settings, click Show hidden files and folders, and then click OK.

Show hidden files in Windows Vista

1. Click Start
   , type control in the Start Search box, and then press Enter.
2. Click Appearance and Personalization.
3. Click Folder Options.
4. Click the View tab.
5. Under Advanced Settings, click Show hidden files and folders, and then click OK.

Show hidden files in Windows XP

1. Start Windows Explorer.
2. On the Tools menu, click Folder Options.
3. Click the View tab.
4. Under Hidden files and folders, click Show hidden files and folders, and then click OK.

Step 1: Exit Outlook

Step 2: Find the Outlook .pst file

1. Click Start
   , type control panel in the Start Search box, and then press Enter.
2. If you see the Control Panel Home view, click User Accounts and Family Safety.
   
   If you do not see the Control Panel Home view, go to step 3.
3. In the Search Control Panel box in the upper-right corner, type mail, and then press Enter.
4. Click Mail or Mail (32-bit). The screen shot for this step is listed below.
   
   
5. Click Data Files. The screen shot for this step is listed below.
   
   
6. Click Personal Folders, and then click Settings.
   
   Note If there are no Personal Folders services in your profile and if you can store information such as messages, contacts, or appointments in Outlook, your information is probably being stored in a mailbox on an Exchange server. If this is true, information is typically backed up on the server. Contact the Exchange server administrator for more information.
7. Write down the text in the Filename box.
   
   Note You may have to click in the Filename box and then use the Right Arrow key to view all the text.
8. Click OK, and then click Close two times.

Step 3: Find the Inbox Repair Tool

1. Use one of the following methods, as appropriate, for the version of Outlook that you are running.
   
   Note If you are unsure what version of Outlook that you use, open Outlook, click the Help menu, and then click About Microsoft Outlook to see the version.
   • Microsoft Office Outlook 2010
     
     Click Start
     , type %ProgramFiles%\Microsoft Office\Office14\ in the Start Search box, and then press Enter.
   • Microsoft Office Outlook 2007
     
     Click Start
     , type %ProgramFiles%\Microsoft Office\Office12\ in the Start Search box, and then press Enter.
     
   • Microsoft Office Outlook 2003
     
     Click Start
     , type %ProgramFiles%\Common Files\System\MSMAPI\1033\ in the Start Search box, and then press Enter.
     
   • Microsoft Outlook 2002
     
     Click Start
     , type %ProgramFiles%\Common Files\System\Mapi\1033\ in the Start Search box, and then press Enter.
     
2. Find and then double-click SCANPST.EXE to start the Inbox Repair Tool.

Step 4: Use the Inbox Repair Tool

1. In the Enter the name of the file you want to scan box, type the path and file name of the Outlook .pst file that you found in step 2.
2. Click Start.
3. After the Inbox Repair Tool operation is complete, click OK.

If you can now read and delete email messages and can click Send/Receive in Outlook without errors, the problem is resolved. If you still receive an error, go to the "Next Steps" section.

Step 1: Exit Outlook

Step 2: Find the Outlook .pst file

1. Click Start, and then click Run.
2. Type control in the Open box, and then press Enter.
3. If you see the Pick a category view, click User Accounts.
   
   If you do not see the Pick a category view, go to step 4.
4. Double-click Mail.
5. Click Data Files.
6. Click Personal Folders, and then click Settings.
   
   Note If there are no Personal Folders services in your profile and if you can store information such as messages, contacts, or appointments in Outlook, your information is probably being stored in a mailbox on an Exchange server. If this is true, information is typically backed up on the server. Contact the Exchange server administrator for more information.
7. Write down the text in the Filename box.
   
   Note You may have to click in the Filename box and then use the Right Arrow key to view all the text.
8. Click OK, and then click Close two times.

Step 3: Find the Inbox Repair Tool

1. Click Start, and then click Search.
2. Click All Files and Folders.
3. In the All or part of the file name box, type Scanpst.exe.
4. Change the selection in the Look in box to the local hard disk. For example, change the selection to Local Disk (C:).
5. Click Search.
6. When the search is complete, double-click SCANPST.EXE to start the Inbox Repair Tool.

Step 4: Use the Inbox Repair Tool

1. In the Enter the name of the file you want to scan box, type the path and file name of the Outlook .pst file that you found in step 2.
2. Click Start.
3. After the Inbox Repair Tool operation is complete, click OK.

If you can now read and delete email messages and can click Send/Receive in Outlook without errors, the problem is resolved. If you still receive an error message, go to the "Next Steps" section.

If the methods that were described earlier do not resolve the problem, you can try creating a new Unicode .pst file, setting it as default, and then importing the data from your older .pst file. For information about how to create a new .pst file and setting it as the default, see the "How to Point Outlook to Your New Personal Folders File" section of following article in the Microsoft Knowledge Base:

To import the original .pst file, it must be removed from the Outlook profile. When Outlook is running, right-click the name of the Outlook data file (.pst) that you want to remove from the Outlook Bar or Navigation Pane, and then click Close name. If the Close command is not available, you are probably trying to remove the default Outlook data file (.pst) that is used to save your new messages. The article that was referenced earlier provides the steps to change the .pst file that is used as the default delivery location.

After you remove the original .pst file from the profile, you can import the data into the new .pst file by using the "How to import .pst file data into Outlook" section of the following article in the Microsoft Knowledge Base:


If these methods did not help you, you may want to ask someone you know for help. Or, if you use Outlook with Exchange Server, you might want to contact the Exchange Server administrator for help. You can also use the Microsoft Customer Support Services website to find other solutions. Some services that the Microsoft Customer Support Services website provides include the following:

• Searchable Knowledge Base: Search technical support information and self-help tools for Microsoft products.
• Solution Centers: View product-specific frequently asked questions and support highlights.
• Other Support Options: Use the web to ask a question, to contact Microsoft Customer Support Services, or to provide feedback.

If you continue to have questions after you use these Microsoft websites or cannot find a solution on the Microsoft Support Services website, go to the Contact Microsoft website.