messages building up

[Mozzi]

Hallo all

I have a server here that is under fairly high load.
My problem is that the messages seem to keep on building up in the mque.in 
directory.
Now I have set the Max Children = 60 as you can see and setup sendmail to 
deque everey 5 mins (sendmail -bd -q15m)

Any ideas how I can get the performance up ?
The server is a dual pIII 800 with 3Gigs ram and a raid5 array
It is running Redhat 7.3 with sendmail (standard) all patches were apllied 
with up2date.
Mailscanner is Version 4.12-2 installed from rpm's
using f-prot

Tnx 

Mozzi