Active Directory doesn't work when impersonate is set to true

[Steve Moreno]

I have a web app that I've developed on an XP Pro workstation and the app
uses AD to grab the user's AD info like address, email, phone, etc... The app
also allows these users to create an Excel file and email it as an attachment
to other selected users.

The problem is this:
On my development workstation everything works fine. The AD works and the
Excel file creation and emailing it works too.

But when I add the <identity impersonate="true"></identityin the
web.config of the Production web server, the Excel file creation works but
the email fails since the AD code doesn't return the user's email address to
plug in to the "FROM" field in the email.

Has anyone seen this AD problem when <identity
impersonate="true"></identityhas been in the web.config file?

Thanks In Advance,
Steve.