If you can recieve but can't send after switching to secure ports you most likely were sent an email between November to now about needing to change your password for your email account. The email was either ignored, marked as spam , maybe deleted? Well anyways, it's locks you out of smtp and if using port 25 it would bypass that security so now that port 25 is closed and you are using 465+ssl or 587+tls it will just keep spamming that you have the wrong password.
So update your password to a new one, update your password in your email client. If it doesn't work immediately wait 5-10 minutes and try again. The new password will work right away but the smtp lock with the old password can possibly take a few minutes to remove (longest wait I have seen is 11 minutes)
Also cox can see it in your account notes if they ever havw sent out that password change notice. So if that notice IS on the account notes and you haven't changed your password then once you change to secure ports you get this exact problem.
(tldr: change your password, wait 5-10 minutes, update your passwords in your email client and you can send again on the secure ports)