Email Limit Reached - Unable to Reduce?

My wife and I are receiving notices that we have exceeded email limits 2Gb? I have deleted large emails from both our email addresses  but continue getting "email stopped" notices from Cox and have got feedback that some emails have not been delivered. I have tried link in email to get intel or support contact. A simple cheat sheet for different clients (outlook, webmail etc) would help us that are savvy but not MIT. Were do I find the current size of my emails vs remaining. I am primary account holder and can't seem to manage email service from account anymore.

Hot tip as a 20+ year customer not needing to wade through "great deals" to get support would be stellar.

Thanx

danot