Using domain name in email address
I have a domain name for my business website and an email address associated with it. For 15 years now, I've set mail up so that emails I send show this email address, rather than my mac.com or me.com address. At some point, one of the OS updates changed that, and there does not seem to be an option for setting mail up this way anymore. Is that true? Do I have to advertise me.com every time i send an email? Is this what Apple is about now? It's not enough that my wife and I have 2 iPhones, 2 iPads, an iPad mini, a MacBook and 4 iMacs between us, we also have serve as advertisements?
iMac, OS X El Capitan (10.11)