My exchange server ran out of space today. The log files in 'exchsrvr\myexchangeserver.log' folder have gone from being a few MB to 5 or 6 GB each. After finding a text editor that could open these log files, I have found loads of entries for a gmail account with an ip address in there. I think this person is somehow relaying from our exchange server.
What should my next steps be to stop these these requests? The log file is currently growing at a rate of about 5MB per minute which still seems way too fast.