Outlook add-in questions

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Hello there,

I am trying to create an add-in for Outlook using the VS.Net 2005 Shared
Add-In project type.

I've progressed far enough to have added a button to the main toolbar and
have it display a messagebox when clicked.

Can anybody explain to me how I can achieve the following:

1 - Move my button so it only shows in a new mail window (ie: when user is
composing an email)
2 - Gain access to the text in the new email and change it (actually encrypt
it)
3 - Check to see if the user's signature has been added to the email (this
will have their public key so need to ensure it is always shown - or created
if none exists for the user and then shown).
4 - How do I intercept the "Send_Click" event that is fired when the user
actually clicks the Send button? I want to check the emails destination, and
then prompt the user to encrypt depending on the destination.

Ultimately I'll do something similar to received emails but decrypt the
message.

I know how to write an external app that creates Outlook messages etc but I
am having trouble figuring out how to access what I am after from inside
Outlook itself, or at least from my add-in...

I hope I have explained this well enough for anyone interested enough to
have a read. Any replies appreciated. Thanks in advance.

Cheers!