There are two ways to reduce memory utilization:
- Reduce the number of scanning processes. I've seen each process consuming up to 400 MB of memory. So, less threads is good. The default is 3. In low volume environments, I've reduced this to 2 processes with no issues. Do this in the Mail Security for Microsoft Exchange Console on the Admin tab.
- Reduce the memory used by each process. In the default configuration, each process uses as much memory as it likes and doesn't give it back. This makes sense on a busy server where that memory is in constant use, but on a relatively quiet server, you want that memory back for other processes. There are registry keys that you can use to set this.
- ProcessUpperMemoryLimitInMB. This key specified the based memory usage for the thread. The thread can use more memory than this when actively processing, but it returns to this level. This value should not be set below 100MB. I typically use 128MB.
- ProcessMemoryCheckTimeInMin. This key specifies when the memory utilization of the threads is reduced. If you do not create and set this key, the default value is 5 minutes.
After changing the registry keys, you must restart Mail Security for Exchange.
Reference post from Symantec includes the path for 64-bit systems if required: