Don't know if this is a 4.2 (Optus) on 8700 thing, but I've just noticed that emails I send on my BB are now exposing my BB's BIS address to my receipients.
I'm on T-Mobile in the UK. What seems to have changed is that the address I put in the BIS as my "Reply to" address now actually only affects that header. Before it used my selected address to populate the "From" header too.
This is BAD news