Greetings,
I looks like this SMG is seeing the memory issue that was addressed in version 10.0.2. I'd suggest updating to the newest version of the SMG (currently 10.5.1) to resolve this issue. I have linked below, a couple of documents that describe the issue and steps you can take to temporarily relieve the symptoms which you are seeing.
Mail processing slows down or stops due to bmserver consuming large amount of memory
http://www.symantec.com/docs/TECH164155
Error fills the logs - IP Freq module: DB open failed: memory mapping error.
http://www.symantec.com/docs/TECH198258