I've always been confused about what tag, tag2 and kill levels mean in SpamAssassin. So, I found the sucker and decided to record. This is from their documentation, but I lost the link.
Mainly, I use this with ISPConfig's interface to Amavis, where they give you a GUI which is pretty straight forward, allowing you to set your spam filtering levels.
SpamAssassin assigns a grade to each message which comes in. This grade can be a negative number (really, really not spam), a zero (not spam) or a positive number (larger numbers are more likely to be spam). The numbers are fairly small; I've rarely seen anything over a 10. SpamAssassin (maybe Amavis) comes with some presets which are something like this:
|Policy||Tag level||Tag2 level||Kill level|
|Wants all spam||3.00||999.00||999.00|
Not very informative tags, and it must be Amavis because SpamAssassin doesn't know about viruses. But, anyway, it is the Tag, Tag2 and Kill Levels we care about for this.
Bascially, if the score is over the Tag level, some headers is put into your e-mail saying it is suspected spam, and you can filter it with rules in your mail client.
If the score is over the Tag2 level and it will modify the Subject, generally putting something like SPAM, usually surrounded by a bunch of asterisks, at the beginning of the subject line.
However, if the score is over the Kill level, the message is never even delivered to you.