Some beginner questions and a lot of "fear"

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Linode DNS Manager

On Linode: a.) Ubuntu 14.04 with Mail in a Box installed. b.) my subdomains, mail.example.com, sub.example.com, sub2.example.com. Google: a.) I registered my domain with Google Domains. b.) My website, example.com, is on Google Cloud Platform. Three DNS Managers, oh my! a.) Linode has a DNS Manager b.) Mail in a Box has a Custom and External DNS webpage c.) Google Domains has a DNS manager I am struggling to configure all three. I am not sure if I even need to configure all three. Any …