It depends on the company. For example Google supports free and open source projects and might like that you contribute to some of them and see if any of them f

It depends on the company. For example Google supports free and open source projects and might like that you contribute to some of them and see if any of them fit their business plan. But yeah you don't want to use company email. When I worked I used my Hotmail account for Microsoft and other tech support and programming websites, so my company email wouldn't get spammed.