A friend recently recommended: http://www.cerberusweb.com
It is a very popular (and affordable) email management solution for help desks & sales teams. It is a bit complex, so you’ll want to take a moment to review the features and consider ways to synthesize it for your business. It appears that everything is managed through email and you have certain email addresses that customers and prospects use (or that it recognizes).
There is workflow, tagging, team resolution, and an integrated knowledge base. Instead of typing an article into the knowledge base, simply answering a client’s problem would give you the ability to ‘Tag’ and file that email into the Knowledge base.
If you’re looking for a Helpdesk+KnowledgeBase combo, this could be a real winner since it integrates tightly with email.