Spam Detectors Compared

Spam Detectors Compared

I often get questions like "Why so many spam detector types?" and "What to choose?".

It's really not easy to answer this question, because it depends on your attitude, the type of mail you get and some other things.

So I try to answer the question the other way round:

What are the advantages and disadvantages of certain Spam detectors?

DNSBLs Yes Low Low Slow No

There are several types of DNSBLs: geographical, by provider, by type and 'know sources of spam'.

The geographical, provider and type based are your choice to use or not to use.

The 'know sources of spam' are somehow a 'political' thing: some DNSBLs list more agressiv while others have a more relaxed listing style. The first one means that occasional you might find an entire large provider listed as source of Spam due to misuse by one of their users (until the provider acts and removes the problem, what can need several days).

Advantage is an 'automated' maintenance by the DNSBL operator.

The speed can depend on cache handling. Caching more IPs will speed up processing, using the progressiv cache will give it an additional boost. But it will raise false positives/false negatives.

Filters No Low Low Fast High

Filters are the winner in speed, flexibility and difficulty.

If you can live with the build-in filters, they are O.K. to use. If you have fun with building your own filters and spend some time and brain, they are very O.K. to use.

If you are a lazy kind of person, they might not be your choice.

Language No Medium High Slow No

The Language Spam detector is a good choice to get rid of certain types of unreadable messages.

The Spam detector is a slow starter, but the speed does not depend on how many languages are selected.

BLAST No Medium High Medium No

BLAST is something you need to try: for most people it works, for some it does not.

If it works, it is a nice and speedy solution.

Blacklist No Low Low Fast Yes

Not really a Spam detector, but the blacklist is a good way to block certain senders of Spam.

Due to the fact that 'real Spammers' change their from-adress, it does not deal very well with these. But for newsletters etc.. it's a good choice.

Scoring High

Not really a Spam detector, too.

It is a combination of all types of Spam detectors. Its main advantage is the very good adaption to any user demands. The major drawbacks are the need for a good concept and the time to implement it.

It might be a choise for 'difficult cases'.


Net traffic Speed
Memory usage Customize by user
CPU usage