According to the Email Diva and their own advertising, Email Analyst is basically the only useful tool on the market for monitoring email activity. Using Email Analyst, organizations that use email marketing can "monitor competitive email offers, see which offers were the most effective in driving traffic to the offer page, monitor affiliate email networks, and find and research new 3rd party lists." It includes an enormous, searchable database of emails (according to their website, nearly 1,000,000 from as far back as 2003). For a quick overview of Email Analyst you can read the E-mail Diva's thoughts, and although there isn't a vast amount of information about the company that makes Email Analyst, Email Data Source, you can check out this article from AmericanVentureMagazine.com. If you're interested, take a look at Email Data Source's website and contact them for a free demonstration.