I’ve used SpamSieve for at least a couple years now, and it is absolutely the one spam solution that just works.
Now that I’ve moved to PostBox 2.5 (yes, it’s in beta, but I noticed this under the earlier versions of PostBox as well), I notice that SpamSieve’s dock icon does not appear whenever e-mail arrives. SpamSieve does do this when running Apple Mail.
Here’s the dumb question: Is SpamSieve still working, even though the icon doesn’t appear?
I’ve not selected for it to be hidden when running.