I was sent an .olm file, downloaded a viewer and it gave me full content to the person’s emails?

So somebody sent me an .olm file and I couldn't open it. I started to download a couple of olm viewers but when I eventually got one to open the file, it opened it and gave me all the contacts and the entire inbox and sent items of this person?

I got a bit of a shock because I feel like I hacked their computer. How could this have happened?

The thing that opened it is called Systools Outlook Mac Exporter