The email reads the following:
If you have not yet upgraded your php you may receive this email. If you have any questions please contact support.

Hello, A recent server scan revealed that your site has a vulnerable version of phpbb. To help ensure the security of the server and your data we are asking you to update your phpbb forum to the latest version. You can find more information on our forums at
http://www.lunarforums.com/forum/viewtopic.php?t=22715 Thank You
Lunarpages Support