about anti-spam for enterprise

[Luca Ferrari]

Dear all,
apologize me if this is not a technical post, but I'd like to get your opinion 
about this. I'm going to set up our enterprise mailserver (of course an 
ubuntu!) to get out the spam e-mails. Now I've got two choices:
1) set up an environment (like spamassassin)
2) buy an antispam appliance

Now I think that setting up a software environment could work as weel as a 
commercial appliance, but I'd like to know if it get too much time to 
configure it to reach good results.
Since I've not experience on this, I'd like to know your opinion about how to 
start.

Thanks,
Luca