Automatically cc myself when sending from 1 particular email account - OSX mail
Currently this isn't possible with the built-in  Mail rule set in Yosemite. As mentioned by user3439894, you have to rely on a third-party utility. Here’s a screenshot from Mail Act-on site. 


You can build your own rule using the additional third-party rule set e.g. Add CC Recipient. So people we see that you have added them to Cc list.