Postfix performance tweaks?

[moba]

I wonder which tweaks we should apply to a potentially busy mailserver with enough resources.

see for example http://www.postfix.org/qmgr.8.html

My ideas so far:

 # i believe this will make a larger cache for recipient caching
 # (use on resourceful machines and for public gateways only)
 qmgr_message_recipient_limit = 50000
 default_recipient_limit = 50000
 # time between attempts to deliver a deferred message (default: 300s)
 minimal_backoff_time = 1000s
 # maximum time between attempts (default: 4000s)
 maximal_backoff_time = 5h
 # time between deferred queue scans (default: 300s)
 queue_run_delay = 1000s