Search Exchange for credit card or social security numbers
A question came up recently at a customer site about how they could search their Exchange mailboxes for email messages that contain credit card numbers. (This is prohibited by their company policy, but they still find credit card numbers occasionally.) Almost immediately after that, someone on a newsgroup asked if it was possible to search all mailboxes using Exchange Server 2010 or 2013 eDiscovery tools for social security numbers.
While searching for text or numerical patterns, such as "XXXX XXXX XXXX XXXX" or XXX-XX-XXXX is a piece of cake for some search engines using regular expressions (RegEx), this is not possible with Exchange eDiscovery tools. I should not that you can do some pattern matching using transport rules and it is possible to intercept messages in transit, but not possible at rest. So, if you are looking for data that is already in your database, then you are somewhat out of luck. At least "out of the box".
Sherpa Software's Discovery Attender does, however, do more complex pattern matching.