Backing up and restoring the AutoComplete cache of Outlook 2010, 2013, 2016, 2019 and Office 365

When I was still using Outlook 2007, I could back up my AutoComplete cache by copying the nk2-file and then reuse it on another computer.

Now that I’m on Office 365, I no longer have this file but the AutoComplete feature still works.

Where is the AutoComplete being cached now and how can I back it up in a way that I can also restore it in the future when needed?

AutoComplete buttonSince Outlook 2010, the AutoComplete cache is being stored within your mailbox itself and is no longer a separate file.

This means that when you are using an Exchange or account, you’ll have the same AutoComplete cache on each computer where you are using Outlook or Outlook on the Web (OWA) to access your mailbox.

For POP3 and IMAP accounts, this is not the case as this information isn’t synchronized with the mail server.


MFCMAPI buttonIn order to backup and restore the AutoComplete cache  you’ll need to make use of MFCMAPI. This is because the AutoComplete information is stored as a “hidden message” within your mailbox or pst-file.

MFCMAPI is a low-level editing tool to access your mailbox data. You can do some really great things with it, but you can also easily do large irreversible damage to your mailbox so it is important that you make a backup first and follow the below instructions carefully.

You can download MFCMAPI from its official development website on GitHub. When you are using the 64-bit version of Outlook, make sure you download the “MFCMAPI.exe.x64” version instead.

It is being developed by Stephen Griffin who is a Senior Escalation Engineer in Developer Support at Microsoft focusing on Outlook and Exchange Server APIs (in other words: this is a very reliable application source).

Backing up the AutoComplete cache

To create a backup of your AutoComplete cache, use the following steps.

  1. Close Outlook. This is important because your AutoComplete cache is being saved when you close Outlook.
  2. Open MFCMAPI.
  3. Accept any dialog prompts to get to the main window of MFCMAPI.
  4. Choose: Session-> Logon…

    MFCMAPI - Session-> Logon... (click on image to enlarge)
    Click on image to enlarge.

  5. Select the mail profile for which you want to change a mailbox’s display name.
    If you are unfamiliar with this dialog, simply press OK.

    Choose Profile dialog box of Outlook.

  6. In the top-part of MFCMAPI you should now see all your configured mailboxes and connected pst-files. Double click on the the mailbox for which you want to backup the AutoComplete list.
  7. In the Navigation Pane on the left, expand the folder list called “Root – Mailbox” or “Root Container”.
  8. Expand the folder list called “Top Information Store”, “IPM_SUBTREE” or “Top of Outlook data file”.
  9. You should now see your Inbox folder. Right click on it and choose: Open associated contents table.

    MFCMAPI - Inbox - Open associated contents table (click on image to enlarge)
    Click on image to enlarge.

  10. In the new dialog that opens up, locate the message with the subject: IPM.Configuration.AutoComplete

    MFCMAPI - Hidden Contents - IPM.Configuration.Autocomplete (click on image to enlarge)
    Click on image to enlarge.

  11. Right click on this message and choose: Export message…
  12. From the “Format to save” dropdown list select “MSG file (UNICODE)” and click OK.
  13. Select the folder where you want to save the message. You are free to rename the file to for instance: AutoComplete-mailboxname.msg
  14. In the CopyTo dialog to set the Interface and Flags, simply press OK.
  15. In the Tags to Exclude dialog, simply press OK as well.
  16. Close all open dialogs to close MFCMAPI or repeat steps 6 to 15 for any other mailbox that you have configured in Outlook and wish to backup the AutoComplete Cache for.

Restoring the AutoComplete cache

To restore your saved AutoComplete cache, use the following steps.

  1. Follow steps 1 to 9 of the backup process mentioned above.
  2. If you already see a message called IPM.Configuration.AutoComplete listed here, export it as explained in the backup section and then delete it from you mailbox:
    1. Right click on the message IPM.Configuration.AutoComplete
    2. Choose: Delete message.
    3. From the Deletion style drop down list select “Permanent deletion (deletes to deleted item retention if supported)” and click OK.
  3. From the menu bar select: Folder-> Import-> From MSG…

    MFCMAPI - Hidden Contents - Import From MSG... (click on image to enlarge)
    Click on image to enlarge.

  4. Browse to and select your saved AutoComplete file and press Open.
  5. Verify that the “Load style” dropdown list is set to: Load message into current folder.
  6. Press OK.
  7. Close all open dialogs to close MFCMAPI or repeat steps 1 to 6 for any other mailbox that you have configured in Outlook and wish to restore the AutoComplete Cache for.

Special note for POP3 accounts

When you are using a POP3 account, you can reuse your original pst-file on another computer or when reconfiguring the account without losing your AutoComplete cache. However, it is important that you do this in the correct way or the list will still be lost.

For instructions see: Restoring a pst-file of a POP3 account on a new computer

Restoring the AutoComplete list from the RoamCache folder

If you no longer have access to your previously configured account but do have a backup of your RoamCache folder, then it may also be possible to still restore your AutoComplete list.

For instructions see: Backup and restore the Outlook’s RoamCache folder

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