I had to do a complete clean install of Yosemite (meaning erase and reinstall every app). Now SpamSieve 2.9.17 attacks two emails for every email selected. Say I choose a single spam email in my inbox and invoke “Train as Spam,” it marks and moves the selected message and the one following it. Same goes for “Train as Good.” If I select 4 emails, 8 are affected.
Had to turn it off again?
Today I attempted to train as good, which moved an extra email into my inbox. I disabled the speed-up preference again and behavior has returned to expected.