I would like to deploy SpamAssassin on a mail server with about 2500
users, but I have found that it runs way too slow. On my 1.3 GHz
machine, it takes 1/3 second per message. That speed is not
acceptable. I want to know if there is a reasonable way to compile
SpamAssassin on Linux, making it run faster. I do know of "compilers"
like perl2exe and PerlApp, which don't really do any compilation, and
HotIce, which optimizes your code, making it run faster. Also, I can't
seem to get the Perl compiler (perlcc) to work right. A free solution
would be wonderful, but a free trial version would allow me to test
this as well. If you believe you have an answer, please try it first
before posting it.

Noodle

Sorry to say, but that's about as good as you're going to get with
Perl.  My past company built a huge perl application (50K lines+) and
speed was one of our motivations to move to Java.

We also didn't have much luck with the perl compiler tools.  

Have you tried turning off some of the real-time blacklist lookups? 
Those could be the cause of your slowdown.

You are running Spamassasin as a daemon, right?

Other solutions include running Exim for SMTP services - it has built
in filtering for spam.

This thread in comp.mail.sendmail discusses performance tuning:
http://groups.google.com/groups?hl=en&lr=&ie=UTF-8&oe=utf-8&threadm=slrnail8d4.5n4.omic%2Busenet4%40johansen.fys.ku.dk&rnum=4&prev=/groups%3Fhl%3Den%26lr%3D%26ie%3DUTF-8%26oe%3Dutf-8%26q%3Dspamassassin%2Bspeed%26sa%3DN%26tab%3Dwg

This thread in muc.lists.debian.user discusses setting up the Daemon
and performance:
http://groups.google.com/groups?hl=en&lr=&ie=UTF-8&oe=utf-8&threadm=20020309034206.GB27196%40birdbrained.org&rnum=2&prev=/groups%3Fhl%3Den%26lr%3D%26ie%3DUTF-8%26oe%3Dutf-8%26q%3Dspamassassin%2Bperformance%2B

As does this thread from linux.debian.user:
http://groups.google.com/groups?hl=en&lr=&ie=UTF-8&oe=utf-8&threadm=20020312024446.GA15912%40earthlink.net&rnum=3&prev=/groups%3Fhl%3Den%26lr%3D%26ie%3DUTF-8%26oe%3Dutf-8%26q%3Dspamassassin%2Bperformance%2B

Let us know what works!