A month ago, I upgraded my older Mac G5 Tower running OSX 10.5.8 Leopard to a new (Late 2011) Macbook Pro running OSX 10.7.2 Lion and updated all my apps including SpamSieve to 2.8.8. F.Y.I. My default Incoming "good mail" sound is "Magic Bell." Everything ran smoothly until a few days ago when mysteriously, all incoming mail would sound Magic Bell immediately followed by the annoying "Brasso" boink sound. I couldn't figure out where it was coming from.
I tried all the usual mac tricks for cleaning and resetting everything that I knew of, but nothing worked. I even set Apple Mail's incoming mail sound preferences to None, but no joy. I contacted Apple Support Community Forums and spent all day going back and forth with guys trying to work through the problem. Finally, an Apple tech tracked down the problem through my Terminal test and detected the sound was coming through SpamSieve. They recommended uninstalling SpamSieve. Instead, I disabled the app by unchecking SpamSieve's Rule in Mail and sure enough, the "Brasso" sound went away.
After all that, it finally dawned on me to check SpamSieve's Preferences. Lo-and-behold!—there was a box—now checked—with Brasso set to sound on incoming mail! I unchecked it and re-enabled SpamSieve. Everything is back to hunky-dory! I have no idea how or why this SpamSieve incoming mail Brasso sound checkbox got checked. I didn't do it. Perhaps it was always there by default. But if it was, why hadn't the double Magic Bell plus Brasso sound combination appeared before? Why did it appear all of a sudden and without my changing anything in my SpamSieve Preferences (which I haven't changed in forever and a day ... or at least since I originally installed the app?)
At any rate, it's fixed now, and I am posting this in the chance that if anyone else out there is encountering the same problem you might read this and not have to waste time hunting for a fix.