Outlook 2016 opens Safari to Search with Google

New Contributor II

I have an instructor using a Mac, running Sierra (10.11.6). Firefox is set as the default browser. Outlook 2016 is the e-mail client. When the instructor highlights and right clicks on a word in an e-mail message, and selects “Search with Google” Outlook opens Safari instead of Firefox. Any ideas why Outlook does not use the default browser setting from the OS? Is there any way to change this behavior? I have not found any browser preference setting in Outlook.