I need to monitor the email traffic at real time, and send alerts out for unusual circumstances. Any way to do this in Scalix? Or some way in sendmail?
I can't think of a way that doesn't require extra development/software.
You can write a perl script that scans the sendmail logs and/or the Scalix audit file for new messages and alert on any anomalies/big messages/etc. I've written something like this for archiving purposes (store the audit log info in a DB backend) and haven't found it very hard.
Another software that does monitoring is cacti which leverages the power of RRDTool. Provides a wide range of graphs, not just bandwidth (for example, disk usage).