AutoComplete feature changes on Outlook 2010 and later versions (Including Outlook 2013 and Outlook 2016)

Outlook 2010 introduced multiple changes in the mechanism of the AutoComplete feature and you should be aware of these changes when using NK2Edit software to edit the AutoComplete files of Outlook 2010.

Here's the list of AutoComplete changes on Outlook 2010:

  • Filename change: In the previous versions of Outlook, the AutoComplete filename was created with .nk2 extension. On Outlook 2010, the filename is created with .dat extension and in the following format: Stream_Autocomplete_0_xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx.dat
    The xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx section is a random 16-bytes hash.

    On a new Outlook installation or new Outlook profile, the Stream_Autocomplete file is created only after the user sends the first email message. Be aware that NK2Edit cannot edit the Autocomplete data until the Stream_Autocomplete file is created in the first time.

  • In additional to the AutoComplete file stored in the local hard drive, another copy of the AutoComplete data is stored inside the message store of Outlook. For MS-Exchange profile, this copy of the AutoComplete data is stored on the Exchange server. For profile based on .pst file, this copy of the AutoComplete data is stored inside the .pst file.

  • If you delete the local AutoComplete file (with .dat extension) or if the user connects the Exchange server from another computer, the AutoComplete data stored in the Exchange server is automatically copied to the local computer.

  • When using the combination of Outlook 2010 (or later) and Exchange Server 2010 (or later), sometimes the AutoComplete data stored on the Exchange server randomly overwrites the changes made with NK2Edit. If you experience the same problem, you can overcome this issue by using the /export_to_message_store command-line option:
    NK2Edit.exe /export_to_message_store $default

    This command-line option copies the local AutoComplete .dat file into the message store of the Exchange Server, to ensure that the older AutoComplete data stored inside the Exchange Server will not overwrite the latest changes you make with NK2Edit.

    Starting from version 2.35, you can also export the AutoComplete data to the message store from the user interface, by using the 'Export To Message Store (Outlook 2010)' option (Ctrl+Shift+M)

    Starting from version 2.37, there is an option to automatically export the AutoComplete data to the message store every time that you save the AutoComplete file. In order to activate it, simply check the 'Automatically Export To Message Store' option located under the Options menu. Starting from version 2.65, You can also do it from command-line together with other command-line options, for example:
    NK2Edit.exe /AutoExportToMessageStore 1 /script "f:\scripts\myscript.txt" $default

  • Outlook allows you to delete the AutoComplete cache completely, from both local AutoComplete file and the message store, by using the following command-line option:
    Outlook.Exe /cleanautocompletecache

    When you use the above command-line option, the AutoComplete file is deleted completely, and NK2Edit will not be able to edit the AutoComplete data until the file is created again by Outlook, after the user sends the first message.

  • Suggested Contacts: Outlook 2010 introduced a new feature known as 'Suggested Contacts', which allows the user to manually add items into the AutoComplete combo-box. Be aware that the 'Suggested Contacts' and the older AutoComplete feature are maintained as 2 separated databases. When the AutoComplete combo-box is opened, the emails list is merged from both data sources.

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