List performance: time to forward one SMTP message with 1000, 2000
and 5000 different remote destinations. Outbound SMTP concurrency
= 100.

dests	1000	2000	5000	time per 1000
=============================================
qmail	15	32	80	16
mx	13	25	(*)	13

(*) message sink host saturated under the load

Local delivery performance: time to deliver 100 SMTP messages to
one recipient. Outbound SMTP concurrency = 100, inbound SMTP
concurrency = 5, 10, 20.

concur	5	10	20	average time
============================================
qmail	62	59	58	60
mx	24	24	25	24

Relay performance: time to forward 100 SMTP messages with one
recipient. Outbound SMTP concurrency = 100, inbound SMTP concurrency
= 5, 10, 20.

concur  5       10      20      average time
============================================
qmail	56	54	54	55
mx	17	19	20	19