How safe is your Email?

The following appeared on the internet:

"Do you think an erased email is gone forever?

We've all sent an embarrassing or unfortunate email and sighed relief when it was finally deleted, thinking the whole episode was behind us. Think again. Just because you delete an email message from your inbox and the sender deletes it from their 'Sent' inbox, does not mean that the email is lost forever. In fact, messages that are deleted often still exist in backup folders on remote servers for years, and can be retrieved by skilled professionals.
So start to think of what you write in an email as a permanent document. Be careful about what you put into writing, because it can come back to haunt you many years after you assumed it was gone forever."