Can't Delete Trash

I hate some parts of the new email program. 

 I keep getting emails from Cox saying I'm nearing my email capacity and need to delete some or risk receiving future emails.  Well if I could....

1) ...Empty trash I'd get rid of over 7000 emails. I've tried opening trash- select all-click the delete icon-choose permanently delete. All emails disappear and page says empty. I then check to see if all are gone and they are all still there! I've also clicked on Empty trash and Clean up. I've deleted history and logged off few times too. Ugh!

2)...Delete my spam folder I wouldn't have to try to remember to delete those emails.  I have settings on no spam filtering. Cox sends personal emails to spam. They don't have a spam subject either. 

Also I am so afraid I'm going to delete an important email because it is checked by Cox. After deleting an email it goes back to inbox and has the next email already checked. I don't want that! Let me choose what needs checking.

Also when inbox is open I select all and go down list unchecking ones I want to keep. All of a sudden the emails turn gray and I lose my place. I also have to make sure Cox didn't check an email I want to keep.

All these problems should be easy to fix by Cox. Frustrating! I better not have my email blocked because I can't delete my trash folder of over 7000 and counting.