Outlook version?
Outlook will only find recipients to whom you have already sent messages at
least once before so that the autocompletion cache is populated.

Signature
Russ Valentine
[MVP-Outlook]
> when I send an email,I've selected the option to have
> Outlook recognize email addresses after I've typed in the
> first few letters. It does it with some name and not
> with others. Does anyone know how to make this work??