Brian Krebs published a valuable post on commercial value for a hacked email account in the underground. In the cybercrime underground many sellers propose collection of hacked email accounts and many cases the offer is profiled according users needs. There are forums specialized in the sale of email accounts for sectors such as defense or industry, meanwhile other commercialize lists also accounts to use for generic phishing attacks. Each email account is a mine of information whose value is understood only when a hacker violate it, but generally is too late to avoid problems.”]
Source: http://securityaffairs.co/wordpress/15205/cyber-crime/business-hacked-email-account.html