A planned outage just means someone in Cox started the maintenance as opposed to an outage based on people calling in or being offline. It does not mean Cox had time before hand to warn their customers like an upgrade but to be honest they rarely alert customers ahead of time for that either.
As for the email address, it does go to the Social Media Team and is in the welcome thread. Even though they might not be able to fix the outage they might be able to tell you something about it. Point is not emailing them DEFINITELY won't help.