RE: Setting Outlook as default application doesn't stick

Hi Squeak825, 

I understand you want to set Outlook 15.3 as the default app on Mac. Unfortunately, our forum only focuses on Office 365 Online services. Since settings for Outlook 15.3 as the default app is an Outlook client behavior, it’s recommended that you post the issue in Outlook for Mac forum for dedicated assistance. Your understanding is appreciated. 

Thanks,
Claud