Exactly. The emails, files and data you generate at work are NOT YOUR PROPERTY. They are the property of your work/institution/funding body.
Everything in those emails is able to be, and IS read by your IT team. It is archived. It is backed up (unless you work for the CRU).
You can be disciplined, fired and PROSECUTED for ANYTHING you put in your emails. Whether they were meant for personal use or not.
This is in the end user agreement everyone signs when you start a new job. I suggest people read it more carefully in the future.