My company, which is quite straight-laced, has a very short email retention policy. Email in your Outlook client is only accessible for 30 days before it gets put into some kind of backup system, where it only has another month or two before it's gone forever.
You can search the backups with a special tool, but it is too painful to do frequently.
You are not allowed to create PST files or otherwise store email locally, in any format. Doing so is a firing offense.
Now, I don't know what they do with the data on the server once it's lost to me. I'm sure they are complying with the law. But they have designed an email system that prevents you from using it as personal long-term storage, as you'd do with your private Gmail account. I always assumed this had to be for liability reasons. It sure is inconvenient, though.