I do not know if this is still open. As it is unanswered, I give you some hints.
try calling the bpstart_notify.cmd manually by hand and watch it closely. Try to find out how long it runs.
The message is clear in this case the bpstart_notify.cmd is simply not returning in the timeout seconds window.
You can configure this timeout, but it should be normally to be 300 seconds (5 minutes). This should be enough. So it should be enough to prepare the mail archive server.