I had few issues dealing Exchange in the times I’ve been charged with its care and feeding. Dealing primarily with version 2000 and some of 2003 it was straight forward in its operation and management. My previous experience with UNIX MTA and MDAs like Postfix and Sendmail (not to mention some Procmail hacking!) gave me the necessary protocol understandings. Bolting on some experience with Active Directory rounded out the knowledge.
In a previous position I was tasked with, and I quote, “all this damned [expletive] big [expletive] SPAM!” on a server with 180 users. I settled on an external appliance that used domain blacklists and Bayesian keyword filter. This involved a change to MX records routing the mail through the appliance and then onto the internal server. I’ll pat myself on the back here and say that through proper planning and understanding I was able to do this without a dropped message in under three hours from opening the box from UPS to end implementation.