There is a distinction between e-mails’ being deleted and a server being wiped. If e-mails are deleted or moved from a server, they appear to no longer exist on the device. But experts say, depending on the condition of the server, underlying data can remain on the device, and the e-mails can often be restored.

To make the information go away permanently, a server must be wiped — a process that includes overwriting the underlying data with gibberish, possibly several times.
That process, according to Platte River Networks, the ­Denver-based firm that has managed the system since 2013, apparently did not happen.

“Platte River has no knowledge of the server being wiped,” company spokesman Andy Boian told The Washington Post. “All the information we have is that the server wasn’t wiped.”