FIXME:

### Parrallel delivery force (local=2 and dest=20 are aggressive)
local_destination_concurrency_limit = 20
default_destination_concurrency_limit = 20

### Max flow rate (1 sec delay per 50 emails/sec over the number of emails delivered/sec)
in_flow_delay = 1s

### Parrallel delivery force (local=2 and dest=20 are default)
local_destination_concurrency_limit = 2
initial_destination_concurrency = 10
default_destination_concurrency_limit = 50

### Limits the mail inflow to 100 messages per second above the number of messages delivered per second.
in_flow_delay = 1s