I am in need of Spam protection for my Linux VPS. I am currently only using IP blocking / RBL.

I am curious what others are using and good / bad experiences. Has anyone tried Postini, Spam Assassin, others...? I've heard that Spam Assassin uses a ton of resources. Any difficulty in installation / configuration?

While SpamAssassin does require a bit more resources it is the industry standard for filtering SPAM emails. You'll just need to tweak it to perform for your environment.

The SpamAssassin wiki has more documentation on Performance related problems:
http://wiki.apache.org/spamassassin/FasterPerformance
http://wiki.apache.org/spamassassin/OutOfMemoryProblems

Postini is probably the most effective SPAM filter I've used, and it has the added benefit of not wasting your VPS' resources. Postini is definitely great for people who are feeling the pinch of one of our Base VPS plans.

<2cents>

Using the resource intensive industry standard may not be the best way to go, but it is the cheapest. Spammers know that this is the 'industry standard' thus are conforming their emails to pass through the free softwares filters. They test the messages against the current rules before sending out their emails. I think using something like postini is best. It is by far the best anti-spam service and they can track and monitor spam from all over the world with their huge userbase.

</2cents>

-Ray

Simply put you can't rely on a single anti-spam measure to be the cure-all for SPAM.

SpamAssassin coupled with real-time black lists, SPF records, and DNS checks, should cut down a vast majority of your SPAM. If you are still getting a ton of SPAM, then I would say that you have probably shared your email address in a public location, and it my be time to just give up on this address, and protect your new email address appropriately.

You might be better off educating your users on best practices with their email address, such as not posting it on public forums, or entering your contact information into untrustworthy sites which might sell your address to solicitors.

Granted there are obviously going to be email addresses that need to be public, and you should expect to get more SPAM on these accounts.

I do agree that Postini is by far the best at this point, and going into the future with Google's experience in large scale networks. That just happens to be my favorite feature of Postini, multiple redundant mail servers ..... mmmmmm.