Versions of eximstats prior to V1.40 used an amount of memory
proportional to the number of log lines being processed. Running over a
very large number of log lines would cause eximstats to use more and more
memory, and the server to run slower and slower, until something gives.
Could this be your problem? Run 'eximstats -h' to determine it's version.
You might be able to verify this if you have a core file to look at, but
I'm not sure how!
Steve