Presidential libraries are depositories of non-classified records pertaining to an administration. Everything a president writes as president, signs, speaks, etc etc is the property of the United States, as well as certain gifts that a president is allowed to use while in office, but may not keep after leaving office. GW for example was allowed to keep bicycles given to him by Trek and Cannondale while he was the president, but they became the property of the USA when he left office, and are maintained and displayed by the National Archives and Records Administation at his presidential library.
Thus, the 'private' blackberries, pseudonym 'social' email accounts and so forth (this has been reported in more than one venue).
These people are liars, obfuscators and perpetrators that leave no tracks - only Executive Orders and haphazard laws that will need to be expunged completely when we get back in power. Their legacy, if there is one, will be a stain on our Constitution where they unfortunately got their hands on it.