I'm trying to get an attachment from an outlook mailbox, but I don't want it to be uploaded to microsoft server for security purposes.

I added the extension point in my xml file:

<ExtensionPoint xsi:type="LaunchEvent">
<LaunchEvents>
<LaunchEvent Type="OnMessageAttachmentsChanged" FunctionName="test" />
</LaunchEvents>
<SourceLocation resid="residUILessFunctionFileUrl" />
</ExtensionPoint> But my test function is only called once the file as been uploaded to the server. I was wondering if I could do and event.preventDefault() before the file is uploaded, but the event returned by the launchevent isn't a normal html event.

Here's my test function:

function test(event){
event.preventDefault() //This isn't possible
console.log(event)
}