false positive

A false positive is a message that has been flagged as spam but is no spam.

There can be different reasons:

• the regular expression filter hit
  (f.x. you have a dirty talk with... hrmpf, a new acquaintance that is not in your Auto-Whitelist )
• the DNSBL is too aggressiv
• ...

It is difficult to avoid false positives. You can check the results of all known DNSBLs with the 'Check DNSBLs' function .

Sidenote: I read variouse mailing lists, some are tech related, some are not. In some of these I have a huge volume of false positives only coming from DNSBLs. In others I have none.

false negative

A false negative is a message flagged as spam that is no spam. Reasons are the same like false positive.