I recently upgraded to El Capitan and noticed that my emails are now being sent from a firstname.lastname@example.org suffix. This is frustrating as I've been using a email@example.com address for years. Friends are now asking why I changed my email which I didn't knowingly do. When I go to the preferences in the mail application I am not able to change my email alias back to the mac.com suffix. In fact the program won't even let me get out of the edit alias dialog box when I try to make a change and I'm forced to quit the program. I tried changing this though the iCloud web platform, which does still allow me the mac.com option but that doesn't seem to help from my desktop based application. Does anyone know how to fix this?