The way it's done is to get everything set on one PC how you want everyone else's to be, then export the registry keys to a file, then set a GPO that applies those keys.
This guide will show example using Outlook 2016 on Windows.
How to set on font settings on one PC
In Outlook File tab click Options > Mail > Stationary and Fonts:
Click on Font and set for New mail messages and Replying or forwarding messages:
How to export registry keys
How to set a GPO to apply the registry keys
You are the expert in GPO. Thus, we will not describe the GPO steps in this guide.
Instead we'll refer to Microsoft KBs and Microsoft community.