The IT people send out the phishing mail themselves as part of a test. It isn’t an actual phishing mail, just something made to look and act like one. In the end they have a report which people fell for it, which ignored it (or were ooo) and which reported it.
Reporting is done via the report phishing feature in Outlook. For consumers it’s sent to Microsoft, but for businesses you can configure those reports to do what you want. It’s actually a really good feature and people should always use it.