Machine slow

[Patrick Chan]

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Hi all,
 
I'm using Redhat 9.0 + MailScanner 4.31.6 + clamav 0.83
I've used MailScanner for a year. Recently, I find that my machine is very slow.
Load average is over 4.0. My users can't receive mail via ipop3d because
from the result of command "top", the CPU resource is used up by MailScanner.
 
When I stop using MailScanner (simply just using sendmail and procmail to block certain file extension), the speed becomes normal, load average drops back to below 1.0
  
I checked maillog, there are many such messages:
MailScanner[8280]: New Batch: Found 31 messages waiting
 
But those 31 messages are not the mails for my users. Those mails seem to be spam mails.

Is there any good solution for this situation? Thanks very much in advance.