Questions regarding the Outlook Security prompt are asked very frequently.
The most complete answer I've seen was provided by Outlook MVP Sue Mosher
and is as follows:

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"The security dialogs that pop up when an application tries to access
certain Outlook properties and methods are designed to inhibit the spread of
viruses via Outlook; see
http://www.slipstick.com/outlook/esecup.htm#autosec. If you are a standalone
user, Outlook provides no way to suppress this behavior. However, you can
use a free tool called Express ClickYes
(http://www.express-soft.com/mailmate/clickyes.html) to click the security
dialog buttons automatically. Beware that this means if a virus tries to
send mail using Outlook or gain access to your address book, it will
succeed.

"If you're the administrator in an Exchange Server environment, you can
reduce the impact of the security prompts with administrative tools. See
http://www.slipstick.com/outlook/esecup/admin.htm

"If it's an application you wrote yourself, you can use one of these
approaches to redo the program:

   -- Use Extended MAPI (see http://www.slipstick.com/dev/mapi.htm) and C++
or Delphi; this is the most secure method and the only one that Microsoft
recommendeds.

   -- Use Redemption (http://www.dimastr.com/redemption/), a third-party
COM library that wraps around Extended MAPI but parallels the Outlook Object
Model

   -- Use SendKeys to "click" the buttons on the security dialogs that your
application may trigger. See
http://www.slipstick.com/outlook/esecup.htm#autosec for a link to sample
code.

   -- Program the free Express ClickYes
(http://www.express-soft.com/mailmate/clickyes.html) tool to start suspended
and turn it on only when your program needs to have the buttons clicked
automatically."

--
Sue Mosher, Outlook MVP
Outlook and Exchange solutions at http://www.slipstick.com
Author of
    Microsoft Outlook Programming: Jumpstart
    for Administrators, Power Users, and Developers
    http://www.slipstick.com/books/jumpstart.htm

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