My company developed an email monitoring system that works by SMTP rountrip testing (i.e. sending emails to the exchange server periodically and making sure they are returned). It works really well and we're working on a multi-tennant version now which is
in beta.
It works with any email system including Exchange, Sendmail, Gmail, and even hosted exchange or pop3 providers. Setup takes about 5-10 minutes.
If anyone's interested in being a beta tester, please let me know.
Elliot
