Of course it is only back up tapes of the email system:

The White House has also admitted that the only safeguard it has to its patently inadequate method for preserving email (dumping them in files that are put on EOP servers) is back-up tape media. These back-up copies, however, are only a “snapshot” of what was on the server at the time of the back-up. In other words they are not comprehensive, as the White House concedes.

Even more troubling, the White House has now admitted that until October 2003, the White House recycled its back-up tapes, which contained the only copies of emails deleted prior to that date. What the White House has not explained is why it changed its policy of preserving all back-up tapes — instituted in March of 2000 when the Clinton administration discovered that its system did not fully preserve all email from the Office of the Vice President — at the same time it decided to dismantle the existing electronic record-keeping system, with no replacement at hand.

Much more at Dkos