any way to encrypt emails

I have a site that collects some personal info from users, and I want to hide the emails.  I can make sure they don't appear on any page, but I also would like to hide them in the database.  So would I just use some standard encryption, or is there some hash technique that hides the email even if a person knows the encryption key?  In the latter case, I would have to be able to send emails to the users, so I can't totally hide it.