Like you, I have no ties with the UCE industry, but here are my guesses regarding this topic. I highly doubt they purge gmail addresses. I still get spam in t

Like you, I have no ties with the UCE industry, but here are my guesses regarding this topic. I highly doubt they purge gmail addresses. I still get spam in there. And incremental costs are so minimal to spammers, that why would they bother? That's kind of the whole reason spam works despite microscopic conversion rates. I also doubt that google shares their anti-spam tech or reports with other mail providers. Each company wants to keep their proprietary stuff secret, and anti-spam tends to have a bit of secret sauce. Now, say google, microsoft, and yahoo got together and shared reputation information, you might see spammers start to avoid those systems (at least from their main botnets) in an effort to not hurt their "reputation". By and large, though, I just think they are willing to spam any address that they think has a small chance of getting to a person. Frequently they're run by bot nets at such small incremental costs. There's no compelling reason for them to do this. FWIW, using the Pivotal Veracity / Returnpath tools (which estimate delivery rates by using seedlists), I've found that MSN is much more likely to mark something as spam, compared with gmail. Weird, I know.