The akka.zeromq.SendHighWatermark option shall set the high water mark for outbound messages on the specified socket.
The high water mark is a hard limit on the maximum number of outstanding messages ØMQ shall queue in memory
for any single peer that the specified socket is communicating with.
If this limit has been reached the socket shall enter an exceptional state and depending on the socket type,
ØMQ shall take appropriate action such as blocking or dropping sent messages.
This is a ZeroMQ 3.0 option