The Contents collection contains all content files. The collection can be used to determine the value of a specific content item, or to iterate through the collection and retrieve a list of all items in the message.
Content = Object.Contents(key|index)
Returns a Content Object
In the following example, a specific content is removed on the Mail_OnStartRender event
Sub Mail_OnStartRender
If Record.Fields("Details") = False Then
Mail.Contents.Remove("Details")
End If
End Sub