Email Notifcations for External Users

I currently have two rules set up in a SharePoint Online list: 

1. "When any item is created, send email to responsible" (Responsible is a column and you can tag a user)

2. "When the status is changed to finished, send email to ____" 

The two rules are currently working for internal users who are members of the site, but not external users. Does SharePoint have a limitation to where these email rules will not work for external users?