You can turn off your email notifications for personal messages by clicking on 'Settings' at the top of your inbox. There is an option to remove email notifications there.
We don't currently have a way of reporting messages that break our guidelines (for example, if they were personal attacks, or a message from a journalist).
This is something we'll definitely look into for the future. In the meantime, if you think a message is something we at GNHQ should take a look at, you can always send us an email at [email protected] letting us know about your concerns.