Outlook 2016 busy not updating
Then, block out your vacation on your own calendar.
When you mark time as "out of office" on your calendar, your coworkers see it when they attempt to schedule a meeting with you.
If you want to share with people outside of your network, you need to publish it on an Internet server (using either HTTP or FTP).
Anonymous users will need Read permissions, you'll need Write permissions on the Internet server.
I believe it was a plugin that handled that feature, but I could be wrong.