This is an attempt to poison your spam filter. By forcing the filter to discriminate between good emails with English text and innocuous words, vs spam emails with English text and slightly different innocuous words, the filter can't discriminate as accurately and may misidentify good emails as spam. In order to combat this we (sometimes implicitly) change the threshold required to flag an email as spam, and allow more spam email through.
Comments
This is an attempt to poison your spam filter. By forcing the filter to discriminate between good emails with English text and innocuous words, vs spam emails with English text and slightly different innocuous words, the filter can't discriminate as accurately and may misidentify good emails as spam. In order to combat this we (sometimes implicitly) change the threshold required to flag an email as spam, and allow more spam email through.
(My guess is this doesn't belong on HN, though.)