mail latency

[Kern, Tom]

Hello, I've been running spamassassin 2.63 with amavis-new 20030616-p9 with 
postfix 3 as a front end for my exchange 2k server for about 4 months now with 
no issue until last week.
now, i have a serious mail latency issue where i sometimes get emails 24hrs 
late.
i've checked exchange and  that doesn't seem to be the issue.
i can't find anything telling in  maillog or messages. where else can i look to 
troubleshoot this issue?
Thanks