Going to try this out tomorrow… will report back my findings.
Good links:
http://www.google.com/support/appsecurity/bin/answer.py?answer=91337
http://www.postini.com/webdocs/activate/msg_security/wwhelp/wwhimpl/common/html/wwhelp.htm?context=msg_security&file=mx_switch_faq.html
http://www.google.com/support/appsecurity/bin/answer.py?answer=91334#order
Sign-up link for Postini’s lowest cost email filtering ($3 per user per year):
http://services.google.com/enterprise/google_msc_purchase?pid=filtering