As much as we'd prefer to encourage dialog from everyone, we can't allow Gmail addresses to be used when registering due to Google's draconian spam policies.
The problem is spammers create Gmail addresses, they then use this to sign up here, our server sends an email to verify addresses, and Google then treats the verification message as spam. Google then downgrades Packetizer's email reputation, thus preventing us from sending normal email to Gmail users.
Nobody else does this to verification messages, so use any other address when signing up other than Gmail.