DECula writes "In a move not communicated to its users beforehand, Google's Gmail servers were reconfigured to not connect to remote pop3 servers that have self-signed certificates, leaving folks with unencrypted connections, or no service when getting email from other services. Not good for the small folks. One suggestion was to allow placing the public keys on Google's side in the user configuration. That would be a heck of a lot better than just dropping users into never never land."
Apparently, "valid" now means "paid someone Google approves to sign the certificate." It's not like commercial CAs have the best security track record