Sending PoisonPill does not lose the messages in the mailbox, PoisonPill is added to the end of the mailbox.  The actor will be able to handle the disconnect in `postStop`.  The design of this is that these actors are completely managed by Play.  If you want another actor outside of the lifecycle of this actor, then you should have another actor somewhere that creates that and manages its lifecycle, and then this actor can forward messages to and from it, including sending a disconnect message from `postStop`.