The problem is how effective they are at killing spam. I'm sure most of us (I still use Gmail) would jump ship in a second if there was a decent alternative tha

The problem is how effective they are at killing spam. I'm sure most of us (I still use Gmail) would jump ship in a second if there was a decent alternative that doesn't force the user to spend time training a local antispam system. Admittedly, Google is really good at that.