Such a feature is available only if you installed Word 2007 and Outlook 2007 together. It's now called Quick Parts.

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Sue Mosher, Outlook MVP
Author of Microsoft Outlook 2007 Programming:
Jumpstart for Power Users and Administrators
http://www.outlookcode.com/article.aspx?id=54
> In some instances in Outlook 2003 you start to type a word like Wednsday and
> Outlook will offer a suggestion that you can use for that word. Usually you
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> different features as autocomplete corrects the word you have already typed.
> Does Outlook 2007 offer this feature?