Spamassassin is slow - any tips or good commercial alternative?

[Charlie]

Thanks for all the replies. In response to some of them:

- we have now installed nscd, so output is now:
# /etc/init.d/nscd status
Status of Name Service Cache Daemon service: running

- we have added 2 more MS children
- we'll look into adding more RAM

> 2-5 seconds per batch is pretty fast. Anything under 1 minute is 
> acceptable IMHO.
> Why the concern about scan times?? Email isn't IM :-). Seriously why the 
> concern about scan times?

The concern is that I am eventually looking to have over 10,000 users, so 
will be receiving, and then sending, multiple emails per second.
Even now, with only 1,500 users, people have started reporting "Too many 
concurrent SMTP connections; Please try again later"
They only started seeing this message after I turned on SpamAssassin. I am 
thinking that perhaps, as 99% of the emails we receive are not spam, that 
scanning for spam may be an unnecessary luxury, once email volumes reach a 
certain level.