Prioritising and managing emails so that we are not dealing with destructive messages?

Answer 1

If you are asking about SPAM, and how to manage and block it, I would recommend the following programs:

Free:
Spam Bayes http://spambayes.sourceforge.net/

Sort-of free:
Ella for Spam Control http://www.openfieldsoftware.com/

Pay:
Cloudmark Desktop http://www.cloudmark.com/desktop/download/

In this case, I think you get what you pay for. Spam Bayes is effective, Ella is a little bit better, and Cloudmark is really excellent.