Many cache hits before message finally delivered

[Daniel Davidson]

I am having an odd problem were simple messages seemingly at random take
a very long time to deliver.  Most others, deliver right away. A little
checking reveals that they are getting scanned for viruses multiple
times.  For example:

[root at mail etc]# grep Nov\ 30 /var/log/maillog|grep 98A1140460 |grep
SpamAssassin\ cache
Nov 30 08:55:29 mail MailScanner[27405]: SpamAssassin cache hit for
message 98A1140460.79963 
Nov 30 08:55:37 mail MailScanner[28156]: SpamAssassin cache hit for
message 98A1140460.25237 
Nov 30 08:55:43 mail MailScanner[28270]: SpamAssassin cache hit for
message 98A1140460.A8B9B
.........
Nov 30 10:12:11 mail MailScanner[11353]: SpamAssassin cache hit for
message 98A1140460.37797 
Nov 30 10:12:15 mail MailScanner[11353]: Requeue: 98A1140460.37797 to
8D23F4033E

This ran about 500 times before the requeue finally took effect.  Any
ideas as to what can cause this?  I just updated clamav, but that does
not seem to help.  Below are the appropriate package versions.  Thanks
for any help in advance.

mailscanner-4.61.7-2
spamassassin-3.3.1-3.el5.rf
clamav-0.96.5-1.el5.rf
postfix-2.3.3-2.1.el5_2
procmail-3.22-17.1