"The messaging interface has returned an unknown error" error message in Outlook 2000 that is installed in Corporate or Workgroup mode

When you check for new mail, send a fax, or create a new Calendar item in Outlook, the attempt is not successful and you receive the following error message: NOTE: Other actions, such as deleting items from the Calendar, Inbox, and Contacts may also generate this error message.

This problem may occur if you have exceeded the built-in .pst size limit. If this is the case, you may be able to work around this problem by using "Allow upgrade to large tables." This feature is available in all versions of Outlook 97 since version 8.03.

For additional information about how to allow upgrades to large tables, click the following article numbers to view the articles in the Microsoft Knowledge Base: If the "Allow upgrade to large tables" does not solve this problem use the following troubleshooting steps:

• Empty the Deleted Items Folder.
• Use the Inbox Repair Tool.
• Create a New Personal Folders (.pst) File.
• Create a New Profile.
• Install a New Set of MAPI files.
• Reinstall Windows.

How to Empty the Deleted Items Folder

If you have a large number of messages in a Microsoft Exchange Server mailbox and you cannot delete them, empty your deleted items folder to resolve this problem. To do this:

1. On the View menu, click Folder List.
2. Right-click Deleted Items, and then click Empty Deleted Items Folder.

How to Use the Inbox Repair Tool

1. Close Outlook.
2. Click Start, point to Settings, and then click Control Panel.
3. Double-click Mail and Fax. (If you do not have the fax service installed, double-click Mail.)
4. On the Services tab, click Personal Folders, click Properties (make note of the information that is in the Path box), and then click OK.
5. Click Start, point to Programs, point to Accessories, point to System Tools, and then click Inbox Repair Tool.
6. In the Drives box, type the path of your Personal Folders file that you noted in step 4, click Start, and then click OK after the scan is complete.
7. Start Outlook and check for new message, send a fax, or create a new Calendar item.

If this does not resolve the problem, continue with the following steps.

How to Create a New Personal Folders (.pst) File

1. Close Outlook.
2. Click Start, point to Settings, and then click Control Panel.
3. Double-click Mail and Fax. (If you do not have the fax service installed, double-click Mail.)
4. On the Services tab, click Personal Folders, click Properties (make note of the information that is in the Path box), and then click OK.
5. On the Services tab, click Personal Folders, and then click Remove.
6. Click Add, click Personal Folders in the Available information services box, and then click OK.
7. In File name box, type your first name. For example, if your name is Bob, type Bob, click Open, click OK twice, and then exit Control Panel.
8. Start Outlook and check for new messages, send a fax, or create a new Calendar item.

If this resolves the problem, you can import your information that is stored in your original Personal Folders (.pst) file.

Use the following steps to import your information:

1. On the File menu, click Import and Export.
2. In the Choose an action to perform box, click Import from a personal folder file (.pst), and then click Next.
3. In the File to import box, type the path of your Personal Folders (.pst) file, and then click Next.
4. Verify that Personal Folders is selected as the folder to import from and the folder to import into, and then click Finish.

If this does not resolve the problem, continue with the following steps.

How to Create a New Profile

1. On the File menu, click Exit and Log Off.
2. Click Start, point to Settings, and then click Control Panel.
3. Double-click Mail and Fax. (If you do not have the fax service installed, double-click Mail.)
4. Click Show Profiles, and then click Add.
5. Click to select the services you use, click Next, and then complete the information for each of the services when you receive the prompt from the Inbox Setup Wizard.
6. When you receive the prompt for the path to your Personal Folder (.pst) file, click before the "M" (without quotation marks) of the Mailbox.pst file, type new, and then click Next.
   
   NOTE: Verify that the path information is not selected before you type new.
7. Complete the steps in the Inbox Setup Wizard.
8. On the General tab, click the name of the profile that you created in the When starting Microsoft Windows Messaging, use this profile box, and then click Close.
9. Start Outlook and check for new messages, send a fax, or create a new Calendar item.

How to Install a New Set of MAPI Files

If the problem is not resolved, use the following steps to install a new set of MAPI files:

1. On the File menu, click Exit and Log Off.
2. Click Start, click Shut Down, click to select the Restart the computer in MS-DOS mode check box, and then click Yes.
3. After your computer restarts, type the following information at the command prompt:
   cd\windows\system
   and then press ENTER.
4. Use the MS-DOS Rename command to change the current name of each of the following files:

        Mapi.dll       Mapi32.dll    Mapisp32.exe    Mapisrvr.exe    Mapiu.dll
        Mapiu32.dll    Mapix.dll     Mapix32.dll     Mspst32.dll     Mapi32x.dll
     

   For example:
   ren Mapi.dll Mapi.old
5. When you finish renaming all of the files above, type cd.., and then press ENTER.
6. Type win, and then press ENTER. This starts Microsoft Windows and any programs in your Startup folder.
7. In Windows, close any programs, click Start, point to Settings, and then click Control Panel.
8. Double-click Add/Remove Programs.
9. Click Microsoft Office or Outlook, click Add/Remove, insert the Office or Outlook CD-ROM into the drive, and then click OK.
10. Click Reinstall in the Setup maintenance program. This installs new copies of the MAPI files.
11. When the Setup program is complete, restart Windows, start Outlook, and check for new messages, send a fax, or create a new Calendar item.

If the problem is not resolved, it is an indication that there are underlying problems in Windows. It may be necessary to reinstall Windows.

For more information about how to perform this task in Windows, see your Windows printed documentation or online Help.