From the AP:

Computer technicians have found 22 million missing White House e-mails from the administration of President George W. Bush and the Obama administration is searching for dozens more days’ worth of potentially lost e-mail from the Bush years, according to two groups that filed suit over the failure by the Bush White House to install an electronic record keeping system.

Read more: http://www.sfgate.com/cgi-bin/article.cgi?f=/n/a/2009/12/14/national/w120825S68.DTL&tsp=1#ixzz0ZhjtALTt

An interesting tidbit from a Jan. 2009 Talking Points Memo article:

But it doesn’t sound like we’ll get everything. The new email system that the White House switched to four years ago allowed all staff members to access storage files and delete messages — unlike the previous system, which was designed to preserve all messages containing official business. Fuchs said that the White House has still declined to make a forensic copy of the records, so any emails that were deleted likely won’t be recovered. And since we’re talking about millions of emails, it may be impossible to know what we don’t have.