SpamAssassin is very configurable. Almost every setting can be configured on a system-wide or user-specific basis.
If SpamAssassin is so good, then why configure it? Well, there are several reasons why it's worth improving spam filtering with SpamAssassin.
SpamAssassin by default (that is, when installed but not customized) typically manages to detect over 80% of spam. After adding a few customizations, the detection rate can be greater than 95%.
Everyone's spam is different and one user's spam might look like another user's ham. By trying to be general, SpamAssassin may fail to filter spam for every user.
Some of the features of SpamAssassin are disabled by default. By enabling them, the spam recognition rate is increased.
The following configuration options are discussed in this chapter: