tracing bottlenecks ?

[lists at sbt.net.au]

I've noticed some of my emails spend up to 5 minutes in amavis checks,
dumb question, how to figure out where is the bottleneck ?

should I try changing max_server = 10 ? or ?

grep amavis /var/log/maillog shows like '980 ms', '912 ms', BUT also:

Oct 29 15:45:22 amavis[21973]: (21973-07) Passed CLEAN {RelayedInternal},
ORIGINATING LOCAL [147.111.222.333]:55095 [147.33.33.44] <ssss at aaaaa.com>
-> <fff at aaaa.com.au>, Queue-ID: 12EBGRT227, Message-ID:
<e4a4cec3-9215-6d92-89b3-41d107a336be at aaa.com>, mail_id: ffgfgarJu, Hits:
-2.898, size: 249274, queued_as: AAAAAA, 300681 ms

'insufficient server resources', or what can I tune ?

TIA, Voytek